cmd/cgo: do not output empty struct for -cdefs

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/9574043
runtime: update comment on stack allocator

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/9665046
A+C: Brian G. Merrell (individual CLA)

Generated by addca.

R=gobot
CC=golang-dev
https://codereview.appspot.com/9797044
effective_go.html: Fix two links
This fixes two intra-page "type assertion" links that were broken in
different ways.

R=golang-dev, dsymonds
CC=golang-dev
https://codereview.appspot.com/9797043

Committer: David Symonds <dsymonds@golang.org>
runtime: flag static variables as no-pointers

Variables in data sections of 32-bit executables interfere with
garbage collector's ability to free objects and/or unnecessarily
slow down the garbage collector.

This changeset moves some static variables to .noptr sections.
'files' in symtab.c is now allocated dynamically.

R=golang-dev, dvyukov, minux.ma
CC=golang-dev
https://codereview.appspot.com/9786044
runtime: introduce cnewarray() to simplify allocation of typed arrays

R=golang-dev, dsymonds
CC=golang-dev
https://codereview.appspot.com/9648044