The package go.net/ipv4 allows to exist a single UDP listener
that join multiple different group addresses. That means that
LocalAddr on multicast UDPConn returns a first joined group
address is not desirable.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6822108

By keeping a single copy of the strings that commonly show up
in headers, we can avoid one string allocation per header.

benchmark                  old ns/op    new ns/op    delta
BenchmarkReadMIMEHeader        19590        10824  -44.75%
BenchmarkUncommon               3168         1861  -41.26%

benchmark                 old allocs   new allocs    delta
BenchmarkReadMIMEHeader           32           25  -21.88%
BenchmarkUncommon                  5            5    0.00%

R=bradfitz, golang-dev, dave, rsc, jra
CC=golang-dev
https://golang.org/cl/6721055

When HTTP bodies were too large and we didn't want to finish
reading them for DoS reasons, we previously found it necessary
to send a FIN and then pause before closing the connection
(which might send a RST) if we wanted the client to have a
better chance at receiving our error response. That was Issue 3595.

This issue adds the same fix to request headers which
are too large, which might fix the Windows flakiness
we observed on TestRequestLimit at:
http://build.golang.org/log/146a2a7d9b24441dc14602a1293918191d4e75f1

R=golang-dev, alex.brainman, rsc
CC=golang-dev
https://golang.org/cl/6826084

Fixes #4092.

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/6819083

The patch adds more cases to agenr to allocate registers later,
and makes 6g generate addresses for sgen in something else than
SI and DI. It avoids a complex save/restore sequence that
amounts to allocate a register before descending in subtrees.

Fixes #4207.

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/6817080

There was an init race between
	check_test.go:init
        universe.go:def
        use of Universe
and
	universe.go:init
        creation of Universe

The order in which init funcs are executed in a package is unspecified.
The test is not currently broken in the golang.org environment
because the go tool compiles the test with non-test sources before test sources,
but other environments may, say, sort the source files before compiling,
and thus trigger this race, causing a nil pointer panic.

R=gri
CC=golang-dev
https://golang.org/cl/6827076

As discussed in issue 2540, nulls are allowed for any type in JSON so they should not result in an error during Unmarshal.
Fixes #2540.

R=rsc
CC=golang-dev
https://golang.org/cl/6759043

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/6821110

Arbitrary decisions: order of the arguments and the
fact it takes a block-type argument (rather than
leaving to user to fill it in later); I'm happy whatever
colour we want to paint it.

We also change DecryptPEMBlock so that it won't
panic when the IV has the wrong size.

R=agl, agl
CC=golang-dev
https://golang.org/cl/6820114

See RFC 1421, section 4.6.1.1

R=agl, agl
CC=golang-dev
https://golang.org/cl/6814104

R=r
CC=golang-dev
https://golang.org/cl/6822111

R=adg, dave
CC=gobot, golang-dev
https://golang.org/cl/6811080

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/6814120

R=golang-dev, r, mikioh.mikioh
CC=golang-dev
https://golang.org/cl/6816080

xtramodes' C_PBIT optimisation transforms:

MOVW          0(R3),R1
ADD           $4,R3,R3

into:

MOVW.P        4(R3),R1

and the AADD optimisation tranforms:

ADD          R0,R1
MOVBU        0(R1),R0

into:

MOVBU        R0<<0(R1),R0

5g does not appear to generate sequences that
can be transformed by xtramodes' AMOVW.

R=remyoudompheng, rsc
CC=golang-dev
https://golang.org/cl/6817085

Otherwise a poorly timed GC can collect the memory before it
is returned to the Go program.

R=golang-dev, dave, dvyukov, minux.ma
CC=golang-dev
https://golang.org/cl/6819119

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6821100

On ARM, char is unsigned, and the code generation for
multiplication gets totally broken.

Fixes #4354.

R=golang-dev, dave, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/6826079

Currently it works incorrectly if user specifies own build tags
and with race detection (e.g. runtime/race is not selected,
because it contains only test files with +build race).

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6814107

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6810102

Performance improvement aside, time.Now() now gets real nanosecond resolution
on supported systems.

Benchmark done on Core i7-2600 @ 3.40GHz with kernel 3.5.2-gentoo.
original vDSO gettimeofday:
BenchmarkNow    100000000               27.4 ns/op
new vDSO gettimeofday fallback:
BenchmarkNow    100000000               27.6 ns/op
new vDSO clock_gettime:
BenchmarkNow    100000000               24.4 ns/op

R=golang-dev, bradfitz, iant, iant
CC=golang-dev
https://golang.org/cl/6814103

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6819117

It also passes on FreeBSD.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6812103

Fixes the test to work correctly on other platforms with
64-bit ints, like Alpha.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6822099

Fixes #4358.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6840043

When exporting a body containing
        x, ok := v.(Type)

the definition for Type was not being included, so when the body
was actually used, it would cause an "unknown type" compiler error.

Fixes #4370.

R=ken2
CC=golang-dev
https://golang.org/cl/6827064

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6813101

R=golang-dev, remyoudompheng, iant, rsc
CC=golang-dev
https://golang.org/cl/6833043

Re-enable the crash tests on NetBSD now that the issue has been
identified and fixed.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6813100

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/6819107

Integrates with the pollserver now.

Uses the old implementation on windows and plan9.

Fixes #2631

R=paul, iant, adg, bendaglish, rsc
CC=golang-dev
https://golang.org/cl/6815049

This is blocking me submitting the net fd timeout
CL, since goapi chokes on my constant.

The much more extensive fix to goapi's type checker
in pending review in https://golang.org/cl/6742050

But I'd rather get this quick fix in first.

R=golang-dev, mikioh.mikioh
CC=golang-dev
https://golang.org/cl/6818104

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6818106

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/6820115

Intel Core 2 Duo (2.16 GHz) running 3.6.5-1-ARCH

benchmark       old ns/op    new ns/op    delta
BenchmarkNow         1856         1034  -44.29%

R=rsc
CC=golang-dev
https://golang.org/cl/6826072

R=golang-dev, r
CC=dvyukov, golang-dev
https://golang.org/cl/6810099

Fixes GOARCH=386 build.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6810098

R=r, dsymonds
CC=golang-dev
https://golang.org/cl/6826070

Fixes #4337.

R=r, minux.ma
CC=golang-dev
https://golang.org/cl/6814098

Fixes #4359.

R=golang-dev, daniel.morsing, rsc
CC=golang-dev
https://golang.org/cl/6834043