spec: add another sentence about BOMs
Although one may argue that they should be legal, gc (at least)
disallows byte order marks that are not the first code point
in the file. Added a sentence to the "Implementation restriction"
clause in the "Source code representation" section to document
this better.

Lifting this restriction (again - the rule has changed at least
twice already) would not break any existing programs, should
we later decide yet again to fiddle the rules about these little
fly specks.

R=golang-dev, dsymonds, gri
CC=golang-dev
https://codereview.appspot.com/8649043
gc: escape unicode BOM in exported string literals

Fixes issue 5260.

R=golang-dev, minux.ma, 0xjnml, r
CC=golang-dev
https://codereview.appspot.com/8658043

Committer: Rob Pike <r@golang.org>
encoding/json: documentation regarding anonymous fields.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/8545046
misc/dist/darwin: add execute bit to preinstall
Fixes issue 5258.

R=golang-dev, iant, minux.ma
CC=golang-dev
https://codereview.appspot.com/8682043