[fixincludes] Fix macOS 10.12 <AvailabilityInternal.h> and <os/trace.h> (PR sanitizer/78267)

[Mike Stump]

On Nov 11, 2016, at 2:15 AM, Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> wrote:
> The patch passes fixincludes make check (this time for real ;-) and
> restores macOS 10.12 bootstrap.

No objections from me.