Move error information into Package struct, so that
a package can be returned even if a dependency failed
to load or did not exist.  This makes it possible to run
'go fix' or 'go fmt' on packages with broken dependencies
or missing imports.  It also enables go get -fix.
The new go list -e flag lets go list process those package
errors as normal data.

Change p.Doc to be first sentence of package doc, not
entire package doc.  Makes go list -json or
go list -f '{{.ImportPath}} {{.Doc}}' much more reasonable.

The go tool now depends on http, which means also
net and crypto/tls, both of which use cgo.  Trying to
make the build scripts that build the go tool understand
and handle cgo is too much work.  Instead, we build
a stripped down version of the go tool, compiled as go_bootstrap,
that substitutes an error stub for the usual HTTP code.
The buildscript builds go_bootstrap, go_bootstrap builds
the standard packages and commands, including the full
including-HTTP-support go tool, and then go_bootstrap
gets deleted.

Also handle the case where the buildscript needs updating
during all.bash: if it fails but a go command can be found on
the current $PATH, try to regenerate it.  This gracefully
handles situations like adding a new file to a package
used by the go tool.

R=r, adg
CC=golang-dev
https://golang.org/cl/5553059

This lets the client of go/build specify additional tags that
can be recognized in a // +build directive.  For example,
a build for a custom environment like App Engine might
include "appengine" in the BuildTags list, so that packages
can be written with some files saying

        // +build appengine   (build only on app engine)

or

        // +build !appengine  (build only when NOT on app engine)

App Engine here is just a hypothetical context.  I plan to use
this in the cmd/go sources to distinguish the bootstrap version
of cmd/go (which will not use networking) from the full version
using a custom tag.  It might also be useful in App Engine.

Also, delete Build and Script, which we did not end up using for
cmd/go and which never got turned on for real in goinstall.

R=r, adg
CC=golang-dev
https://golang.org/cl/5554079

R=ken2
CC=golang-dev
https://golang.org/cl/5573047

        Fixes #2454.

R=rsc, mikioh.mikioh, golang-dev, iant, iant
CC=golang-dev
https://golang.org/cl/5557068

Golden files have extension .d.golden where d is the mode value (0 or 1 for now)
(i.e., testdata/file.out is now testdata/file.0.golden, and there is a new file
testdata/file.1.golden for each testcase)

R=rsc
CC=golang-dev
https://golang.org/cl/5573046

for map iteration.  New code makes table output predictable and fixes
bug.

R=rsc, r
CC=golang-dev
https://golang.org/cl/5573044

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5562047

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5571046

Google contributor.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/5554084

So it's not included in the package by the go tool.

R=iant, fullung, rsc
CC=golang-dev
https://golang.org/cl/5563049

Document that indirection through a nil pointer will panic.
Explain function invocation.
This section will need more work, but it's a start.

Fixes #1865.
Fixes #2252.

R=rsc, iant, r
CC=golang-dev
https://golang.org/cl/5532114

R=adg, rsc, r
CC=golang-dev
https://golang.org/cl/5562051

Fixes #2674.

R=rsc
CC=golang-dev
https://golang.org/cl/5574045

Fixes #2582

R=rsc
CC=golang-dev
https://golang.org/cl/5574044

R=rsc
CC=golang-dev
https://golang.org/cl/5555071

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5561060

R=rsc, nigeltao
CC=golang-dev
https://golang.org/cl/5561056

R=rsc
CC=golang-dev
https://golang.org/cl/5555070

iant's idea.

Fixes #2745.

R=iant, dsymonds
CC=golang-dev
https://golang.org/cl/5536085

Invaluable when changing template files.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5571044

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5564045

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5564046

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5571043

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5569043

Marshalling of []byte in attributes and the general
marshalling of named []byte types was fixed.

A []byte field also won't be nil if an XML element
was mapped to it, even if the element is empty.

Tests were introduced to make sure that *struct{}
fields works correctly for element presence testing.
No changes to the logic made in that regard.

R=rsc
CC=golang-dev
https://golang.org/cl/5539070

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5568043

R=adg
CC=golang-dev
https://golang.org/cl/5554073

R=rsc
CC=golang-dev
https://golang.org/cl/5529055

It was 2^31, but that could cause overflow and trouble.
Reduce it to 2^30 and add a TODO.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/5562049

I haven't looked at the source, but the gc compiler appears to
omit "not used" errors when there is an error in the
initializer.  This is harder to do in gccgo, and frankly I
think the "not used" error is still useful even if the
initializer has a problem.  This CL tweaks some tests to avoid
the error, which is not the point of these tests in any case.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5561059

        Their last use is removed in rev 70ed048caad2.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5532115

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5532118

It takes too much memory to be reliable and causes
trouble on 32-bit machines.
Sigh.

Fixes #2756.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5567043

R=r, dave, r
CC=golang-dev
https://golang.org/cl/5533086

Make the panic detectable, and use that in ioutil.ReadFile to
give an error if the file is too big.

R=golang-dev, minux.ma, bradfitz
CC=golang-dev
https://golang.org/cl/5563045

R=rsc
CC=golang-dev
https://golang.org/cl/5556077

Fixes #2654.

R=rsc
CC=golang-dev
https://golang.org/cl/5545058

R=rsc
CC=golang-dev
https://golang.org/cl/5555066

This fixes the bug Rob ran into when editing package bytes.
Regexp imports regexp/syntax, which imports bytes, and
regexp/syntax was not being properly recompiled during a
test of a change to package bytes.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5555065

R=rsc, imkrasin
CC=golang-dev
https://golang.org/cl/5554066