syscall: document that documentation is platform specific

Fixes issue 4051

R=golang-dev, minux.ma, rsc
CC=golang-dev
https://codereview.appspot.com/6943063

Committer: Shenghou Ma <minux.ma@gmail.com>
api/next.txt: update

R=golang-dev, rsc, bradfitz
CC=golang-dev
https://codereview.appspot.com/6935061
net/http/pprof: fix doc for /debug/pprof/
Fixes issue 4548.

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/6944053
os: fix docs for Expand
there is no concept of “undefined” variables for Expand。

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/6946063
net/smtp: remove data race from TestSendMail.

A data race was found in TestSendMail by the race detector.

Fixes issue 4559.

R=golang-dev, bradfitz, dave, rsc
CC=golang-dev
https://codereview.appspot.com/6944057

Committer: Russ Cox <rsc@golang.org>
test: add "duplicate" struct map key test

Update issue 4555.

R=gri, iant
CC=golang-dev
https://codereview.appspot.com/6944059
runtime: implement getenv for Plan 9

With this change the runtime can now read GOMAXPROCS, GOGC, etc.

I'm not quite sure how we missed this.

R=seed, lucio.dere, rsc
CC=golang-dev
https://codereview.appspot.com/6935062

Committer: Russ Cox <rsc@golang.org>
cmd/cgo: access errno from void C function
Fixes issue 3729.

R=rsc
CC=golang-dev
https://codereview.appspot.com/6938052
syscall: lazily populate the environment cache on Plan 9

This decreases the amount of system calls during the
first call to Getenv. Calling Environ will still read
in all environment variables and populate the cache.

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/6939048
fmt, encoding/gob: fix misuse of Read
reader.Read() can return both 0,nil and len(buf),err.
To be safe, we use io.ReadFull instead of doing reader.Read directly.

Fixes issue 3472.

R=bradfitz, rsc, ality
CC=golang-dev
https://codereview.appspot.com/6285050
cmd/gc: add GOEXPERIMENT=zerostack to clear stack on function entry

This is expensive but it might be useful in cases where
people are suffering from false positives during garbage
collection and are willing to trade the CPU time for getting
rid of the false positives.

On the other hand it only eliminates false positives caused
by other function calls, not false positives caused by dead
temporaries stored in the current function call.

The 5g/6g/8g changes were pulled out of the history, from
the last time we needed to do this (to work around a goto bug).
The code in go.h, lex.c, pgen.c is new but tiny.

R=ken2
CC=golang-dev
https://codereview.appspot.com/6938073
exp/types: completed typechecking of parameter passing

Details:
- fixed variadic parameter passing and calls of the form f(g())
- fixed implementation of ^x for unsigned constants x
- fixed assignability of untyped booleans
- resolved a few TODOs, various minor fixes
- enabled many more tests (only 6 std packages don't typecheck)

R=rsc
CC=golang-dev
https://codereview.appspot.com/6930053
net/http: fix goroutine leak in error case

Fixes issue 4531

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/6937069
time: fix panic with time.Parse(time.StampNano, ... )

Fixes issue 4502.

R=rsc
CC=golang-dev
https://codereview.appspot.com/6949058
debug/elf: handle missing shstrndx in core files

Fixes issue 4481.

hello-world-core.gz was generated with a simple hello world c program and core dumped as suggested in the issue.

Also: add support for gz compressed test fixtures.

R=minux.ma, rsc, iant
CC=golang-dev
https://codereview.appspot.com/6936058
cmd/6g: fix componentgen for funarg structs.

Fixes issue 4518.

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/6932045
exp/gotype: disable failing tests and add a few more

R=rsc, alex.brainman
CC=golang-dev
https://codereview.appspot.com/6948066
go/doc: add "hdr-" prefix to headers generated from package overviews.

R=golang-dev, bradfitz, gri
CC=golang-dev
https://codereview.appspot.com/6935071