syscall: Use NewError for all system errors and introduce
        some new errors for compatibility with other packages
        and proper error handling in net. Also introduce
        Temporary and Timeout methods on ErrorString.

net: Make errors from dial, accept, listen functions follow the
        OpError standard and discern whether the underlying
        error came from syscall. Since Plan 9 uses a correspondence
        between file and network operations, all system error
        reporting happens through the underlying file operation.
        In Go code, we go through package os for file operations,
        so there is another level of indirection in error types.
        This change allows us to compare the errors with those in
        package syscall, when appropriate.

os: Just use the error string already present in package os,
        instead of calling out to package syscall.

R=rsc, ality, rminnich, bradfitz
CC=golang-dev
https://golang.org/cl/7398054

Map order is non-deterministic. Introduce a new
environment string array that tracks the env map.
This allows us to produce identical results for
Environ() upon successive calls, as expected by the
TestConsistentEnviron test in package os.

R=rsc, ality, rminnich, bradfitz, r
CC=golang-dev
https://golang.org/cl/7411047

The installer package will now detect a previous installation and warn the user
that the previous installation will be deleted. If the user continues, the
installer will delete the previous installation and install the package as
usual.

Fixes #4293.

R=adg
CC=golang-dev
https://golang.org/cl/7427044

Generated by addca.

R=gobot
CC=golang-dev
https://golang.org/cl/7432043

R=golang-dev, r, bradfitz, iant
CC=golang-dev
https://golang.org/cl/7407050

It's not a big deal, but it's easy to fix.

R=dsymonds
CC=dr.volker.dobler, golang-dev
https://golang.org/cl/7425043

New tests added for port handling and IDNA domains.
A new test case contains several redundant
tests but provides a nice documentation of the
implemented rules for domain handling.

R=nigeltao
CC=golang-dev
https://golang.org/cl/7393070

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7230059

Fixes #4873.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7421043

Update #4842

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7369060

Also delete bogus tests for f.pkg (does the file have a package) since all
files have a package attached. The tests for pkg.types and pkg.values
suffice.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/7418043

These are superseded by the tool at misc/dist.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7420044

R=r
CC=golang-dev
https://golang.org/cl/7375060

Permits all sorts of custom HTTP timeout policies without
adding a new Transport timeout Duration for each combination
of HTTP phases.

This keeps track internally of which TCP connection a given
Request is on, and lets callers forcefully close the TCP
connection for a given request, without actually getting
the net.Conn directly.

Additionally, a future CL will implement res.Body.Close (Issue
3672) in terms of this.

Update #3362
Update #3672

R=golang-dev, rsc, adg
CC=golang-dev
https://golang.org/cl/7372054

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/7420043

Fixes #4897.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/7377061

R=adonovan
CC=golang-dev
https://golang.org/cl/7369059

Use portable ReadDirent, not linux Getdents.

R=gri
TBR=gri
CC=golang-dev
https://golang.org/cl/7405051

ssadump:
- permit naming a package (not just *.go files) on command line.
- set BuildSerially flag when setting Log* flags
  (Q. should instead the logging functions take a lock?)

Builder:
- fixed bug when calling variadic function with zero '...'-params.
  Added regression test.

interp:
- more external functions:
   the 'error' interface
   bytes.{Equal,IndexByte}
   reflect.(Value).{Bool,NumOut,Out}
   syscall.{Close,Fstat,Read,Open,Stat,Lstat,Fstat,
     Getdents,ParseDirents,Getwd}
- permit comparisons between *Function and *closure.

With this CL, ssadump can now interpret ssadump itself (!),
loading, parsing, typing, SSA-building, and running
println("Hello, World!").  While a fmt-based equivalent still
lacks some external routines, e.g. math/big, I think there are
diminishing returns in expanding the interpreter (and
debugging it is starting to feel like "Inception").

I'm pretty confident this package is now good enough for wider use.

R=gri
CC=golang-dev
https://golang.org/cl/7392053

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7392054

Add DialOpt. So we have:

func Dial(net, addr string) (Conn, error)
func DialTimeout(net, addr string, timeout time.Duration) (Conn, error)
func DialOpt(addr string, opts ...DialOption) (Conn, error)

DialTimeout (and Dial) are regrettable in retrospect. Maybe
in a future Go we'll be back down to one Dial, with DialOpt
becoming Dial.

DialOpt looks like:

c, err := net.DialOpt("google.com:80")  // tcp is default
c, err := net.DialOpt("google.com:80", net.Timeout(30 * time.Second))
c, err := net.DialOpt("google.com:80", net.TCPFastOpen())
c, err := net.DialOpt("google.com:80", net.LocalAddr(..))
c, err := net.DialOpt("google.com:53", net.Network("udp6"))

And then: (clustered in godoc)

type DialOption interface { /* private only */ }
  func Deadline(time.Time) DialOption
  func LocalAddr(Addr) DialOption
  func Network(string) DialOption
  func TCPFastOpen() DialOption
  func Timeout(time.Duration) DialOption

I'm pretty confident we could add Happy Eyeballs to this too.

Fixes #3097
Update #3610
Update #4842

R=golang-dev, r, dave, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/7365049

add per-P cache of dead G's
add global runnable queue (not used for now)
add list of idle P's (not used for now)

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7397061

If all locals are optimized away, the type instructions would stay in the instruction stream. Call fixautoused to scrub the output.

Fixes #4915.

R=rsc
CC=golang-dev
https://golang.org/cl/7385055

The values for the planet masses are given in
earth mass, not solar mass.

R=golang-dev, dave, r
CC=golang-dev
https://golang.org/cl/7368054

Update #3362

R=golang-dev, adg, rsc
CC=golang-dev
https://golang.org/cl/7369055

While submitting CL 7371051 I accidentally reverted much of CL
7395052.  This change restores it.

R=gri
TBR=gri
CC=golang-dev
https://golang.org/cl/7364051

R=rsc
CC=golang-dev
https://golang.org/cl/7383054

The correct semantics of named result parameters and deferred
procedures cannot be implemented with the existing Ret
instruction alone, since the required sequence is:
(1) evaluate return operands and parallel-assign them to
    named result parameters
(2) invoke deferred procedures
(3) load named result parameters to form result tuple.

We introduce a new 'rundefers' instruction that explicitly
invokes the deferred procedure calls, and we generate code
that follows the sequence above.

Most functions do not use deferred procedures but this cannot
be known in a single pass.  So, we add an optimisation to
eliminate redundant 'rundefers'; it is piggybacked on the
existing pass done for "lifting".

Added tests.

R=gri
CC=golang-dev
https://golang.org/cl/7411043

Details:
- move Builder.nTo1Vars into package => thread-safe.
- add BuildSerially builder mode flag to disable concurrency.
- add Builder.BuildAllPackages method.

Benchmark: BuildAllPackages for $GOROOT/test/append.go drops
to 83ms from 190ms (GOMAXPROCS=8).

R=gri
CC=golang-dev
https://golang.org/cl/7371051

R=r, dave
CC=golang-dev
https://golang.org/cl/7403055

which was submitted earlier.

R=r
CC=golang-dev
https://golang.org/cl/7402048

Fixes #3349.

R=bradfitz, dave, minux.ma
CC=golang-dev
https://golang.org/cl/7383056

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/7401053

The current code uses 64-bit pc-relative on 64-bit systems,
but in ELF linkers there is no such thing, so we cannot
express this in a .o file. Change to 32-bit.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7383055

This CL changes the encoding used for the Go symbol table,
stored in the binary and used at run time. It does not change
any of the semantics or structure: the bits are just packed
a little differently.

The comment at the top of runtime/symtab.c describes the new format.

Compared to the Go 1.0 format, the main changes are:

* Store symbol addresses as full-pointer-sized host-endian values.
  (For 6g, this means addresses are 64-bit little-endian.)

* Store other values (frame sizes and so on) varint-encoded.

The second change more than compensates for the first:
for the godoc binary on OS X/amd64, the new symbol table
is 8% smaller than the old symbol table (1,425,668 down from 1,546,276).

This is a required step for allowing the host linker (gcc) to write
the final Go binary, since it will have to fill in the symbol address slots
(so the slots must be host-endian) and on 64-bit systems it may
choose addresses above 4 GB.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7403054

R=dr.volker.dobler
CC=golang-dev
https://golang.org/cl/7389048

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/7376058

And one real leak in TimeoutHandler.

Fixes #4821

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/7369056

- better documentation of Check
- better handling of (explicit) internal panics
- gotype: don't stop after 1st error

R=adonovan, r
CC=golang-dev
https://golang.org/cl/7406052

Fixes #3348.

R=devon.odell, minux.ma, bradfitz, mdempsky
CC=golang-dev
https://golang.org/cl/7406050