cmd/go: fix capitalization of Bitbucket, document Git support

Fixes issue 5226.

R=golang-dev, minux.ma, iant
CC=golang-dev
https://codereview.appspot.com/8320044

Committer: Shenghou Ma <minux.ma@gmail.com>
misc: update zsh completion

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/8437043

Committer: Shenghou Ma <minux.ma@gmail.com>
runtime: reset typed dangling pointer
If for whatever reason seh points into Go heap region,
the dangling pointer will cause memory corruption during GC.
Update issue 5193.

R=golang-dev, alex.brainman, iant
CC=golang-dev
https://codereview.appspot.com/8402045
runtime: reset dangling typed pointer
+untype it because it can point to different types
Update issue 5193.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/8454043
runtime: replace union in MHeap with a struct
Unions break precise GC.
Update issue 5193.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/8368044
runtime: replace unions with structs
Unions can break precise GC.
Update issue 5193.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/8456043
runtime: change Lock from union to struct
Unions can break precise GC.
Update issue 5193.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/8457043
runtime: change Note from union to struct
Unions can break precise GC.
Update issue 5193.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/8362046
runtime: make CgoMal alloc field void*

This makes it an unsafe.Pointer in Go so the garbage collector
will treat it as a pointer to untyped data, not a pointer to
bytes.

R=golang-dev, dvyukov
CC=golang-dev
https://codereview.appspot.com/8286045
runtime: fix deadlock in network poller
The invariant is that there must be at least one running P or a thread polling network.
It was broken.
Fixes issue 5216.

R=golang-dev, bradfitz, r
CC=golang-dev
https://codereview.appspot.com/8459043
runtime: gofmt -s

R=golang-dev, iant, dave
CC=golang-dev
https://codereview.appspot.com/8253045

Committer: Dave Cheney <dave@cheney.net>