Also fixes plan9 cross-build.

R=rsc, r
CC=golang-dev
https://golang.org/cl/5675073

Fixes #2844.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5675072

R=golang-dev, r, r
CC=golang-dev
https://golang.org/cl/5674067

Sigh.

R=golang-dev, gri, nigeltao
CC=golang-dev
https://golang.org/cl/5675071

This revolutionary transfiguration undergirding the code base
Fixes #2945.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/5676072

The set of errors forwarded by the os package varied with system and
was therefore non-portable.
Three helpers added for portable error checking: IsExist, IsNotExist, and IsPermission.
One or two more may need to come, but let's keep the set very small to discourage
thinking about errors that way.

R=mikioh.mikioh, gustavo, r, rsc
CC=golang-dev
https://golang.org/cl/5672047

/tmp being itself a symlink causes problems for the test, so use / as the absolute path.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/5675070

Invalid return statements were accidentally compiling or
triggering internal errors.
Fixes #3044.

R=golang-dev, rsc
CC=golang-dev, remy
https://golang.org/cl/5673074

Complete list of tokens that can start a top-level expression.

R=rsc
CC=golang-dev
https://golang.org/cl/5671074

Fixes #3031.

R=golang-dev, rsc, r, iant
CC=golang-dev
https://golang.org/cl/5676054

Update some other docs too.

Update #2955.

R=rsc
CC=golang-dev
https://golang.org/cl/5676060

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5671072

Fixes #3042.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/5675067

It was being skipped due to an oversight.
Also adjust naming parameters for map type construction - makes debugging easier.
Prelude to issue 3026.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5674071

Fixes #2950.
Fixes #2951.

R=golang-dev, r
CC=golang-dev, remy
https://golang.org/cl/5672044

It depended on the old behavior of functions in structs.

R=golang-dev, rsc
CC=golang-dev, r
https://golang.org/cl/5656076

NewFile take uintptr
make syscall.ProcAttr.Files be []uintptr

R=rsc
CC=golang-dev
https://golang.org/cl/5656073

Clang 3.1 has more warnings enabled by default than GCC.
Combined with -Werror, they cause the build to fail
unnecessarily.  if the name of our compiler ends in "clang",
add the necessary extra -Wno options.  Ideally we would add
these flags unconditionally, as GCC is supposed to ignore
unknown -Wno flags, but apple's llvm-gcc doesn't.

Fixes #2878.

R=rsc, dave
CC=golang-dev
https://golang.org/cl/5673055

Periodically browse MHeap's freelists for long unused spans and release them if any.

Current hardcoded settings:
        - GC is forced if none occured over the last 2 minutes.
        - spans are handed back after 5 minutes of uselessness.

SysUnused (for Unix) is a wrapper on madvise MADV_DONTNEED on Linux and MADV_FREE on BSDs.

R=rsc, dvyukov, remyoudompheng
CC=golang-dev
https://golang.org/cl/5451057

struct literals.

R=gri
CC=golang-dev
https://golang.org/cl/5653073

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/5674070

R=golang-dev, nigeltao
CC=golang-dev
https://golang.org/cl/5676064

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5674069

The previous link worked, but was unnecessary and had a trailing "}".

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5674068

Part of issue 2573.

R=dsymonds, golang-dev
CC=golang-dev
https://golang.org/cl/5674064

Fixes #2573.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5676063

R=golang-dev
TBR=dsymonds
CC=golang-dev
https://golang.org/cl/5673064

Updates #2946.

R=golang-dev, r, r
CC=golang-dev
https://golang.org/cl/5671061

Updates #2573.

R=golang-dev, dsymonds, r
CC=golang-dev
https://golang.org/cl/5677063

Update #2946.

R=golang-dev, bradfitz, bradfitz
CC=golang-dev
https://golang.org/cl/5674065

TBR=r
CC=golang-dev
https://golang.org/cl/5676062

An unindented XML example is hard to follow. MarshalIndent
allows moving the example over to a test file (and fixing it).

R=golang-dev, r, gustavo, r, rsc
CC=golang-dev
https://golang.org/cl/5674050

TBR=r
CC=golang-dev
https://golang.org/cl/5671060

Update #2573.

R=r
CC=golang-dev
https://golang.org/cl/5656071

R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/5677060

It depended on old behavior of functions in structs.
Solved by adding a boolean method to check .Run != nil.

R=golang-dev, adg, r, rsc
CC=golang-dev
https://golang.org/cl/5674062

R=bradfitz
CC=golang-dev
https://golang.org/cl/5673061

R=gri
CC=golang-dev
https://golang.org/cl/5677061

go/doc: move Examples to go/ast
cmd/go: use go/doc to read examples
src/pkg: update examples to use new convention

This is to make whole file examples more readable. When presented as a
complete function, preceding an Example with its output is confusing.
The new convention is to put the expected output in the final comment
of the example, preceded by the string "output:" (case insensitive).

An idiomatic example looks like this:

// This example demonstrates Foo by doing bar and quux.
func ExampleFoo() {
        // example body that does bar and quux

        // Output:
        // example output
}

R=rsc, gri
CC=golang-dev
https://golang.org/cl/5673053

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5656070