Back out previous; otto saw a potential race that could lead to a
authortb <tb@openbsd.org>
Tue, 28 Jun 2016 06:40:11 +0000 (06:40 +0000)
committertb <tb@openbsd.org>
Tue, 28 Jun 2016 06:40:11 +0000 (06:40 +0000)
commitb6a4d1cc42b243fc298114297c0ae97e63148b0b
treec61d733359f40b72d757fde607a4db540cb07e1b
parentffb670e3b5e1a115fbe0ced147b3326a08d33542
Back out previous; otto saw a potential race that could lead to a
double unmap and I experienced a much more unstable firefox.

discussed with otto on icb
lib/libc/stdlib/malloc.c