Use the unified syntax when generating assembly for clang. The clang 3.5
integrated assembler only accepts it.

MFC after:	1 week
Sponsored by:	ABT Systems Ltd
Apply the same fix in r274697 to the ARM case.
Merge remote-tracking branch 'freebsd/master' into hardened/current/master
Merge remote-tracking branch 'origin/hardened/current/master' into hardened/current/segvguard