Add AO primitives implementation to GC based on C11 atomic intrinsic

Add AO primitives implementation to GC based on C11 atomic intrinsic

* Makefile.direct (SRCS): Add include/private/gc_atomic_ops.h.
* include/include.am (dist_noinst_HEADERS): Likewise.
* include/private/gc_atomic_ops.h: New file; define needed AO entities
if GC_BUILTIN_ATOMIC, otherwise include atomic_ops.h.
* include/private/gc_locks.h [THREADS && GC_PTHREADS
&& !GC_WIN32_THREADS]: Include gc_atomic_ops.h instead of atomic_ops.h.
* include/private/gc_priv.h [PARALLEL_MARK || THREADS && MPROTECT_VDB]:
Likewise.
* include/private/specific.h: Likewise.
* pthread_stop_world.c: Include private/gc_atomic_ops.h instead of
atomic_ops.h.
* tests/subthread_create.c: Likewise.
* thread_local_alloc.c [THREAD_LOCAL_ALLOC && GC_GCJ_SUPPORT]: Likewise.
* typd_mlc.c [GC_FORCE_INCLUDE_ATOMIC_OPS || GC_BUILTIN_ATOMIC]:
Likewise.
* win32_threads.c [GC_DLL && !GC_NO_THREADS_DISCOVERY && !MSWINCE]:
Likewise.