exp/locale/collate: first changes that introduce implementation of tailorings:
- Elements in the array are now sorted as a linked list.  This makes it easier to
  apply tailorings.
- Added code to sort entries by collation elements.
- Added logical reset points.  This is used for tailoring relative to certain
  properties, rather than characters.

NOTE: all code for type entry should now be in order.go.  To keep the diffs for
this CL reasonable, though, the existing code is left in builder.go.  I'll move
this in a separate CL.

R=r
CC=golang-dev
http://codereview.appspot.com/6493063
exp/locale/collate: Added functionality to parse and process LDML files
for both locale-specific exemplar characters and tailorings to
the collation table.
Some specifices:
- Moved stringSet to the beginning of the file and added some functionality
  to parse command line files.
- openReader now modifies the input URL for localFiles to guarantee that
  any http source listed in the generated file is indeed this source.
- Note that the implementation of the Tailoring API used by maketables.go
  is not yet checked in. So for now adding tailorings are simply no-ops.
- The generated file of exemplar characters will be used somewhere else.
  Here is a snippet of how the body of the generated file looks like:

type exemplarType int
const (
        exCharacters exemplarType = iota
        exContractions
        exPunctuation
        exAuxiliary
        exCurrency
        exIndex
        exN
)

var exemplarCharacters = map[string][exN]string{
        "af": [exN]string{
                0: "a á â b c d e é è ê ë f g h i î ï j k l m n o ô ö p q r s t u û v w x y z",
                3: "á à â ä ã æ ç é è ê ë í ì î ï ó ò ô ö ú ù û ü ý",
                4: "a b c d e f g h i j k l m n o p q r s t u v w x y z",
        },
        ...
}

R=r
CC=golang-dev
http://codereview.appspot.com/6501070
strconv: faster FormatFloat for fixed number of digits.

The performance improvement applies to the case where
prec >= 0 and fmt is 'e' or 'g'.

Additional minor optimisations are included. A small
performance impact happens in some cases due to code
refactoring.

benchmark                              old ns/op    new ns/op    delta
BenchmarkAppendFloat64Fixed1                 623          235  -62.28%
BenchmarkAppendFloat64Fixed2                1050          272  -74.10%
BenchmarkAppendFloat64Fixed3                3723          243  -93.47%
BenchmarkAppendFloat64Fixed4               10285          274  -97.34%

BenchmarkAppendFloatDecimal                  190          206   +8.42%
BenchmarkAppendFloat                         387          377   -2.58%
BenchmarkAppendFloatExp                      397          339  -14.61%
BenchmarkAppendFloatNegExp                   377          336  -10.88%
BenchmarkAppendFloatBig                      546          482  -11.72%

BenchmarkAppendFloat32Integer                188          204   +8.51%
BenchmarkAppendFloat32ExactFraction          329          298   -9.42%
BenchmarkAppendFloat32Point                  400          372   -7.00%
BenchmarkAppendFloat32Exp                    369          306  -17.07%
BenchmarkAppendFloat32NegExp                 372          305  -18.01%

R=golang-dev, rsc
CC=golang-dev, remy
http://codereview.appspot.com/6462049
cmd/go: be clear that import loops are bad

There was mail on golang-nuts a few weeks ago
from someone who understood the message perfectly
and knew he had a cyclic dependency but assumed
that Go, like Python or Java, was supposed to handle it.

R=golang-dev, bradfitz, dave
CC=golang-dev
http://codereview.appspot.com/6488069
cmd/6g, cmd/8g: eliminate short integer arithmetic when possible.

Fixes issue 3909.
Fixes issue 3910.

R=rsc, nigeltao
CC=golang-dev
http://codereview.appspot.com/6442114
cmd/gc: Suggest *T in error for x.(T) if it would work.

Accomplished by synchronizing the formatting of conversion errors between typecheck.c and subr.c

Fixes issue 3984.

R=golang-dev, remyoudompheng, rsc
CC=golang-dev
http://codereview.appspot.com/6500064

Committer: Russ Cox <rsc@golang.org>
cmd/ld: support zero-filled section for Mach-O files

R=golang-dev, r, dave, rsc
CC=golang-dev
http://codereview.appspot.com/6492069
A+C: add Uriel Mangado (individual CLA)

R=golang-dev, r
CC=golang-dev
http://codereview.appspot.com/6492070
codereview.py: correct error handling without decorator

The decorator hides the number of function arguments from Mercurial,
so Mercurial cannot give proper error messages about commands
invoked with the wrong number of arguments.

Left a 'dummy' hgcommand decorator in place as a way to document
what functions are hg commands, and just in case we need some other
kind of hack in the future.

R=adg, rsc
CC=golang-dev
http://codereview.appspot.com/6488059

Committer: Russ Cox <rsc@golang.org>
cmd/gc: fix PkgPath of byte, rune types

Fixes issue 3853.

R=ken2
CC=golang-dev
http://codereview.appspot.com/6492071