Fixes #6293.

Image "testdata/benchRGB-interlace.png" was generated by opening "testdata/benchRGB.png" in the editor Gimp and saving it with interlacing enabled.

Benchmark:
BenchmarkDecodeRGB        	     500	   7014194 ns/op	  37.37 MB/s
ok  	pkg/image/png	4.657s

BenchmarkDecodeInterlacing	     100	  10623241 ns/op	  24.68 MB/s
ok  	pkg/image/png	1.339s

LGTM=nigeltao
R=nigeltao, andybons, matrixik
CC=golang-codereviews
https://golang.org/cl/102130044

(This is a patch from the pkgsrc Go package.)

LGTM=iant
R=golang-codereviews, iant, joerg.sonnenberger, dave
CC=golang-codereviews, joerg
https://golang.org/cl/108340043

debug/elf: add (*File).DynamicSymbols, ErrNoSymbols, and tests for (*File).Symbols and (*File).DynamicSymbols, and formalize symbol order.

Added a complement to (*File).Symbols for the dynamic symbol table.
Would be useful, for instance, if seraching for certain shared objects
compatible with certain libraries (for instance, LADSPA requires an
exported symbol "ladspa_descriptor").

Added a variable ErrNoSymbols that canonicalizes a return from
(*File).Symbols and (*File).DyanmicSymbols if the file has no symbols.

Added tests for both (*File).Symbols and (*File).DynamicSymbols;
there was never a test for (*File).Symbols at all. A small C program using
libelf, included in the test data, was used to produce the golden
symbols to compare against.

As part of the requirements for testing, (*File).Symbols and (*File).DynamicSymbols now document the order in which the symbol tables are returned (in the order the symbols appear in the file).

All tests currently pass.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/107530043

The builder builds with GOROOT_FINAL=/usr/local/go set.

TBR=rsc
R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/112100043

Also detect GOARCH automatically based on `uname -m`.

LGTM=crawshaw, dave, rsc
R=rsc, iant, crawshaw, dave
CC=golang-codereviews
https://golang.org/cl/111780043

LGTM=dave, rsc
R=rsc, iant, dave
CC=golang-codereviews
https://golang.org/cl/109390043

LGTM=dave, rsc
R=rsc, iant, dave
CC=golang-codereviews
https://golang.org/cl/101590044

It uses an unsupported addressing mode.

LGTM=iant, rsc
R=rsc, iant
CC=golang-codereviews
https://golang.org/cl/106370043

LGTM=dave, rsc
R=rsc, iant, dave
CC=golang-codereviews
https://golang.org/cl/101620043

LGTM=dave, rsc
R=rsc, iant, dave
CC=golang-codereviews
https://golang.org/cl/110330044

LGTM=rsc
R=rsc, iant, dave
CC=golang-codereviews
https://golang.org/cl/103680046

LGTM=dave, rsc
R=rsc, iant, dave
CC=golang-codereviews
https://golang.org/cl/108360043

LGTM=adg
R=adg
CC=dustmop, golang-codereviews
https://golang.org/cl/111000044

Fixes #8174.

LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/102360043

Fixes #8224.

LGTM=alex.brainman, rsc
R=alex.brainman, rsc, dave
CC=golang-codereviews
https://golang.org/cl/104200046

Found using the vet check in CL 106370045.

This is a second attempt at CL 101670044, which omitted the deps_test change.

This adds dependencies to net/rpc:

        encoding
        encoding/base64
        encoding/json
        html
        unicode/utf16

The obvious correctness and security warrants the additional dependencies.

LGTM=rsc
R=r, minux, rsc, adg
CC=golang-codereviews
https://golang.org/cl/110890043

Generated by a+c.

R=gobot
CC=golang-codereviews
https://golang.org/cl/110970047

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/105100044

LGTM=iant
R=bradfitz, iant
CC=golang-codereviews
https://golang.org/cl/112010045

LGTM=minux, bradfitz
R=golang-codereviews, minux, bradfitz
CC=golang-codereviews
https://golang.org/cl/104650043

LGTM=dave, iant
R=iant, dave
CC=golang-codereviews
https://golang.org/cl/112000043

When we've switched to 8K pages,
heap started to grow by 128K instead of 64K,
because it was implicitly assuming that pages are 4K.
Fix that and make the code more robust.

LGTM=khr
R=golang-codereviews, dave, khr
CC=golang-codereviews, rsc
https://golang.org/cl/106450044

LGTM=minux
R=minux
CC=golang-codereviews
https://golang.org/cl/107640044

LGTM=0intro, dave
R=dave, 0intro
CC=golang-codereviews
https://golang.org/cl/106560044

Also remove arch-specific Go files in the Plan 9 syscall package

LGTM=0intro
R=0intro, dave
CC=ality, golang-codereviews, jas, mischief, rsc
https://golang.org/cl/112720043

LGTM=0intro
R=0intro
CC=ality, dave, golang-codereviews, jas, mischief, rsc
https://golang.org/cl/104570043

size instead of abusing text symbol

cmd/addr2line needs to know the virtual address of the start
of the text segment (load address plus header size). For
this, it used the text symbol added by the linker. This is
wrong on amd64. Header size is 40 bytes, not 32 like on 386
and arm. Function alignment is 16 bytes causing text to be
at 0x200030.

debug/plan9obj now exports both the load address and the
header size; cmd/addr2line uses this new information and
doesn't rely on text anymore.

LGTM=0intro
R=0intro, gobot, ality
CC=ality, golang-codereviews, jas, mischief
https://golang.org/cl/106460044

LGTM=0intro, r
R=0intro, r
CC=ality, golang-codereviews, jas, mischief
https://golang.org/cl/108420043

LGTM=0intro, r
R=0intro, r
CC=ality, dave, golang-codereviews, jas, mischief, rsc
https://golang.org/cl/111910043

LGTM=0intro, r
R=0intro, r
CC=ality, dave, golang-codereviews, jas, mischief, rsc
https://golang.org/cl/105580044

NetlinkRIB is currently allocating a page sized slice of bytes in a
for loop and it's also calling Getpagesize() in the same for loop.

This CL changes NetlinkRIB to preallocate the page sized slice of
bytes before reaching the for loop. This reduces memory allocations
and lowers the number of calls to Getpagesize() to 1 per NetlinkRIB
call.

This CL reduces the allocated memory from 141.5 MB down to 52 MB in
a test.

LGTM=crawshaw, dave
R=dave, dsymonds, crawshaw
CC=bradfitz, dsymonds, golang-codereviews
https://golang.org/cl/110920043

Fixes #8165.

After this change, the panic is replaced by a message:

        $ go build -o out ...doesntexist
        warning: "...doesntexist" matched no packages
        no packages to build

The motivation to return 1 exit error code is to allow -o flag
to be used to guarantee that the output binary is written to
when exit status is 0. If someone uses an import path pattern
to specify a single package and suddenly that matches no packages,
it's better to return exit code 1 instead of silently doing nothing.
This is consistent with the case when -o flag is given and multiple
packages are matched.
It's also somewhat consistent with the current behavior with the
panic, except that gave return code 2. But it's similar in
that it's also non-zero (indicating failure).
I've changed the language to be similar to output of go test
when an import path pattern matches no packages (it also has a return status of
1):

        $ go test ...doesntexist
        warning: "...doesntexist" matched no packages
        no packages to test

LGTM=adg
R=golang-codereviews, josharian, gobot, adg
CC=golang-codereviews
https://golang.org/cl/107140043

LGTM=bradfitz, minux
R=bradfitz, golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/110940043

http://gcc.gnu.org/PR61746

http://code.google.com/p/gofrontend/issues/detail?id=35

LGTM=crawshaw
R=golang-codereviews, crawshaw
CC=golang-codereviews
https://golang.org/cl/111980043

LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/108450044

LGTM=bradfitz
R=golang-codereviews, bradfitz, minux
CC=golang-codereviews
https://golang.org/cl/110400043

Maxstring is not updated in the new string routines,
this makes runtime think that long strings are bogus.
Fixes #8339.

LGTM=crawshaw, iant
R=golang-codereviews, crawshaw, iant
CC=golang-codereviews, khr, rsc
https://golang.org/cl/110930043

LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/104600043

LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/107600043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/107590043