This reverts commit 80590711.

Conflicts:
	src/runtime/proc1.go (resolved by hand)

Change-Id: Ic62e3e802f0007ff9012b37bc5fd41fcafc153d0
Reviewed-on: https://go-review.googlesource.com/3885Reviewed-by: Dmitry Vyukov <dvyukov@google.com>