runtime: revert 3c2cddfbdaec
runtime: revert 3c2cddfbdaec

It appears, syscall.NewCallback still
uses heap to store executable code.

R=golang-dev, khr
CC=golang-dev
https://codereview.appspot.com/9060046

apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,apparentlymart/golang,apparentlymart/golang,tv42/old-go,tv42/old-go,gnanderson/go,tv42/old-go,gnanderson/go,gnanderson/go,apparentlymart/golang,pombredanne/go-deleteme,gnanderson/go,apparentlymart/golang,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,apparentlymart/golang,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,gnanderson/go,apparentlymart/golang