in emacs go mode.  Thanks Alex Shinn for the patch.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5728063

Also add some more MAC tests.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5728065

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5730061

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5727068

CL 3075041 says ARM is not little-endian, but my test suggests otherwise.
My test program is:

    package main
    import ("fmt"; "syscall"; "os")
    func main() {
       err := syscall.Fallocate(1, 1/*FALLOC_FL_KEEP_SIZE*/, 0, int64(40960));
       fmt.Fprintln(os.Stderr, err)
    }

Without this CL, ./test > testfile will show: file too large; and strace shows:
    fallocate(1, 01, 0, 175921860444160)    = -1 EFBIG (File too large)
With this CL, ./test > testfile will show: <nil>; and strace shows:
    fallocate(1, 01, 0, 40960)              = 0

Quoting rsc:
"[It turns out that] ARM syscall ABI requires 64-bit arguments to use an
(even, odd) register pair, not an (odd, even) pair. Switching to "big-endian"
worked because it ended up using the high 32-bits (always zero in the tests
we had) as the padding word, because the 64-bit argument was the last one,
and because we fill in zeros for the rest of the system call arguments, up to
six. So it happened to work."

I updated mksyscall_linux.pl to accommodate the register pair ABI requirement,
and removed all hand-tweaked syscall routines in favor of the auto-generated
ones. These including: Ftruncate, Truncate, Pread and Pwrite.

Some recent Linux/ARM distributions do not bundle kernel asm headers,
so instead we always get latest asm/unistd.h from git.kernel.org (just like
what we do for FreeBSD).

R=ken, r, rsc, r, dave, iant
CC=golang-dev
https://golang.org/cl/5726051

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5726062

Fixes #3196.

R=golang-dev, rsc
CC=golang-dev, remy
https://golang.org/cl/5725044

R=lvd, gri
CC=golang-dev
https://golang.org/cl/5731061

R=ken2
CC=golang-dev
https://golang.org/cl/5728064

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5729068

Fixes #3189.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5730058

Fixes #3191.
Sorry.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5726059

An X.509 path length constrains the number of certificate that may
follow in the chain. This is a little simplistic for a first pass as it
doesn't check self-signed certificates (which don't count towards the
length), but it's conservatively simplistic.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5727057

asn1 didn't have an omitempty tag, so the list of additional primes in
an RSA private key was serialised as an empty SEQUENCE, even for
version 1 structures. This tripped up external code that didn't handle
v2.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5729062

UTCTime only has a two digit date field and year values from 50 should
be 1950, not 2050.

R=golang-dev, r, rsc
CC=golang-dev
https://golang.org/cl/5729063

R=rsc, golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5732053

This CL changes the behavior of Dial and Listen API family.

Previous Dial and Listen allow a combo of "tcp6" and IPv4 or IPv6
IPv4-mapped address as its argument, but it also makes slightly
different behaviors between Linux and other platforms. This CL fixes
such differences across over platforms by tweaking IP-level socket
option IPV6_V6ONLY. Consequently new Dial and Listen API family will
reject arguments consists of "tcp6" and IPv4 or IPv6 IPv4-mapped
address.

This CL also adds a bit clarified unicast listener tests.

Fixes #2581.

R=rsc, minux.ma
CC=golang-dev
https://golang.org/cl/5677086

The motivation for this CL is to support $GOPATH well.
Since we already have a FileSystem interface, implement a
Plan 9-style name space.  Bind each of the $GOPATH src
directories onto the $GOROOT src/pkg directory: now
everything is laid out exactly like a normal $GOROOT and
needs very little special case code.

The filter files are no longer used (by us), so I think they
can just be deleted.  Similarly, the Mapping code and the
FileSystem interface were two different ways to accomplish
the same end, so delete the Mapping code.

Within the implementation, since FileSystem is defined to be
slash-separated, use package path consistently, leaving
path/filepath only for manipulating operating system paths.

I kept the -path flag, but I think it can be deleted too.

Fixes #2234.
Fixes #3046.

R=gri, r, r, rsc
CC=golang-dev
https://golang.org/cl/5711058

The current package comment doesn't mention varints and
protocol buffers. Also, the first sentence is incomprehensible
without further context as "fixed-size values" is undefined.

R=rsc
CC=golang-dev
https://golang.org/cl/5715048

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5729065

R=golang-dev
CC=golang-dev
https://golang.org/cl/5730053

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5732059

R=golang-dev, dsymonds, bradfitz, minux.ma
CC=golang-dev
https://golang.org/cl/5732058

R=golang-dev, kyle, r
CC=golang-dev
https://golang.org/cl/5728055

R=golang-dev, kyle, r, bradfitz
CC=golang-dev
https://golang.org/cl/5729053

R=golang-dev, minux.ma, r
CC=golang-dev
https://golang.org/cl/5728051

R=golang-dev, r, minux.ma
CC=golang-dev
https://golang.org/cl/5738045

Fixes #3076.

R=golang-dev, dsymonds, r
CC=golang-dev
https://golang.org/cl/5727056

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5729061

        We have 'gofmt' and 'go fmt', but not 'go tool fmt'.

R=golang-dev, kyle, r
CC=golang-dev
https://golang.org/cl/5739043

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5730051

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5727052

R=golang-dev, kyle, r
CC=golang-dev
https://golang.org/cl/5729052

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5727054

Fixes #3177

R=adg
CC=golang-dev
https://golang.org/cl/5728057

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5732056

Fixes #3176.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5737043

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5729054

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5731056

Missed a case for variadic functions with too few arguments.
The code passes, and with the right error, but might as well record the test case.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5732050