* omp-general.c (omp_context_name_list_prop): New function.
	(omp_context_selector_matches): Use it.  Return 0 if it returns
	NULL.
	(omp_context_selector_props_compare): Allow equivalency of an
	identifier and a string literal containing no embedded zeros.
c-family/
	* c-omp.c (c_omp_check_context_selector): Handle name lists
	containing string literals.  Don't diagnose atomic_default_mem_order
	with multiple props.
c/
	* c-parser.c (c_parser_omp_context_selector): Rename
	CTX_PROPERTY_IDLIST to CTX_PROPERTY_NAME_LIST, add CTX_PROPERTY_ID.
	Use CTX_PROPERTY_ID for atomic_default_mem_order, only allow a single
	identifier in that.  For CTX_PROPERTY_NAME_LIST, allow identifiers
	and string literals.
cp/
	* parser.c (cp_parser_omp_context_selector): Rename
	CTX_PROPERTY_IDLIST to CTX_PROPERTY_NAME_LIST, add CTX_PROPERTY_ID.
	Use CTX_PROPERTY_ID for atomic_default_mem_order, only allow a single
	identifier in that.  For CTX_PROPERTY_NAME_LIST, allow identifiers
	and string literals.
	* pt.c (tsubst_attribute): Fix up STRING_CST handling if allow_string.
testsuite/
	* c-c++-common/gomp/declare-variant-2.c: Adjust expected diagnostics,
	add a test for atomic_default_mem_order with a string literal.
	* c-c++-common/gomp/declare-variant-3.c: Use string literal props
	in a few random places, add a few string literal prop related tests.
	* c-c++-common/gomp/declare-variant-8.c: Likewise.
	* c-c++-common/gomp/declare-variant-9.c: Use string literal props
	in a few random places.
	* c-c++-common/gomp/declare-variant-10.c: Likewise.
	* c-c++-common/gomp/declare-variant-11.c: Likewise.
	* c-c++-common/gomp/declare-variant-12.c: Likewise.
	* g++.dg/gomp/declare-variant-7.C: Likewise.

From-SVN: r278202