Dedupe _GNU_SOURCE and ucontext.h definition and inclusion, put them in sane locations.

Change-Id: Ib61db11ec1a00ca675820da8dc916f7ce03e445e
audio: Unhide PCM offload enums

Change-Id: Iab074ae64d293781769032cc902e72a93374679f
Merge "Dedupe _GNU_SOURCE and ucontext.h definition and inclusion, put them in sane locations." into du44
Merge pull request #1 from DirtyUnicorns-KitKat/du44

merged