runtime: prepare for 8K pages Ensure than heap is PageSize aligned.
runtime: prepare for 8K pages
Ensure than heap is PageSize aligned.

LGTM=iant
R=iant, dave, gobot
CC=golang-codereviews
https://codereview.appspot.com/56630043

pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme