OpenMP: Support acquires/release in 'omp require atomic_default_mem_order'

This is an OpenMP 5.2 feature.

gcc/c/ChangeLog:

	* c-parser.cc (c_parser_omp_requires): Handle acquires/release
	in atomic_default_mem_order clause.
	(c_parser_omp_atomic): Update.

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_omp_requires): Handle acquires/release
	in atomic_default_mem_order clause.
	(cp_parser_omp_atomic): Update.

gcc/fortran/ChangeLog:

	* gfortran.h (enum gfc_omp_requires_kind): Add
	OMP_REQ_ATOMIC_MEM_ORDER_ACQUIRE and OMP_REQ_ATOMIC_MEM_ORDER_RELEASE.
	(gfc_namespace): Add a 7th bit to omp_requires.
	* module.cc (enum ab_attribute): Add AB_OMP_REQ_MEM_ORDER_ACQUIRE
	and AB_OMP_REQ_MEM_ORDER_RELEASE
	(mio_symbol_attribute): Handle it.
	* openmp.cc (gfc_omp_requires_add_clause): Update for acquire/release.
	(gfc_match_omp_requires): Likewise.
	(gfc_match_omp_atomic): Handle them for atomic_default_mem_order.
	* parse.cc: Likewise.

gcc/testsuite/ChangeLog:

	* c-c++-common/gomp/requires-3.c: Update for now valid code.
	* gfortran.dg/gomp/requires-3.f90: Likewise.
	* gfortran.dg/gomp/requires-2.f90: Update dg-error.
	* gfortran.dg/gomp/requires-5.f90: Likewise.
	* c-c++-common/gomp/requires-5.c: New test.
	* c-c++-common/gomp/requires-6.c: New test.
	* c-c++-common/gomp/requires-7.c: New test.
	* c-c++-common/gomp/requires-8.c: New test.
	* gfortran.dg/gomp/requires-10.f90: New test.
	* gfortran.dg/gomp/requires-11.f90: New test.