Add OMP_STANDALONE_CLAUSES.

Add OMP_STANDALONE_CLAUSES.

	gcc/
	* tree.h (OMP_STANDALONE_CLAUSES): New macro.
	* gimplify.c (gimplify_omp_workshare): Use it.
	gcc/c/
	* c-parser.c (c_parser_oacc_enter_exit_data): Use
	OMP_STANDALONE_CLAUSES.
	gcc/cp/
	* parser.c (cp_parser_oacc_enter_exit_data): Use
	OMP_STANDALONE_CLAUSES.

From-SVN: r222580