A+C: Add Janne Snabb.

R=iant
CC=gofrontend-dev
https://codereview.appspot.com/7329044
runtime: Do not reserve huge amount of swap on 32 bit architectures.

The mmap() call which reserves the arena should have MAP_NORESERVE
flag as in typical cases this memory will never be (fully) needed.
This matters in environments which do not do Linux style memory
overcommit, such as OpenIndiana/OpenSolaris/Solaris.

The MAP_NORESERVE flag does not exist on all operating systems
(for example FreeBSD). Therefore we define it to zero value in
case it does not exist.

Fixes issue 21.

R=golang-dev, minux.ma, iant, dave
CC=gofrontend-dev, golang-dev
https://codereview.appspot.com/7310094

Committer: Ian Lance Taylor <iant@golang.org>