cmd/ld: generate relocated DWARF in hostobj mode

While we're here, downgrade DWARF to version 2.
We're not using any version 3 features, and OS X gdb
only supports version 2.

Fixes issue 3436.

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/7891044
cmd/ld: fix typo

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/7552045
debug/dwarf: support for DWARF 3

R=rsc
CC=golang-dev
https://codereview.appspot.com/7662045
runtime: prevent garbage collection during hashmap insertion

Inserting a key-value pair into a hashmap storing keys or values
indirectly can cause the garbage collector to find the hashmap in
an inconsistent	state.

Fixes issue 5074.

R=golang-dev, minux.ma, rsc
CC=golang-dev
https://codereview.appspot.com/7913043
bytes,strings: remove user name from BUG in comment

R=golang-dev, dave
CC=golang-dev
https://codereview.appspot.com/7856048
cmd/gc: implement revised rule for shifts in equality.

R=rsc, daniel.morsing
CC=golang-dev
https://codereview.appspot.com/7613046
doc/go1.1.html: add links to the text, write some new sections

R=golang-dev, rsc, dave
CC=golang-dev
https://codereview.appspot.com/7914043
cmd/5l: fix arm build

Fixes build. One part of ../misc/cgo/test appears to be unhappy but this does not cause the build to fail.

R=rsc, r
CC=golang-dev
https://codereview.appspot.com/7769047
net/http: new benchmark to measure server without network

No net package involved. And with ReportAllocs we can see
how much garbage is created per request.

R=adg, dave
CC=golang-dev
https://codereview.appspot.com/7913044
cmd/ld: remove remaining occurrence of isobj.

Fixes cgo builds.

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/7784044
cmd/6c, cmd/8c: fix stack allocated Biobuf leaking at exit

Fixes issue 5085.

{6,8}c/swt.c allocates a third Biobuf in automatic memory which is not terminated at the end of the function. This causes the buffer to be 'in use' when the batexit handler fires, confusing valgrind.

Huge thanks to DMorsing for the diagnosis.

R=golang-dev, daniel.morsing, rsc
CC=golang-dev
https://codereview.appspot.com/7844044
misc/swig: remove old broken Makefile

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/7786046
net/http/fcgi: Request.Body should always be non-nil

Found this inconsistency from net/http's Server while
debugging Issue 4183

Unfortunately this package lacks testing around this,
or most of child.go. :/

R=golang-dev, adg
CC=golang-dev
https://codereview.appspot.com/7735046
runtime: prevent garbage collection during hashmap insertion (fix 2)

Fixes issue 5074 in multi-threaded scenarios.

R=golang-dev, daniel.morsing, dave, dvyukov, bradfitz, rsc
CC=golang-dev, remyoudompheng
https://codereview.appspot.com/7916043