openmp: Add macros for iterator element access

openmp: Add macros for iterator element access

gcc/c/

	* c-parser.cc (c_parser_omp_iterators): Use macros for accessing
	iterator elements.
	(c_parser_omp_clause_affinity): Likewise.
	(c_parser_omp_clause_depend): Likewise.
	(c_parser_omp_clause_map): Likewise.
	(c_parser_omp_clause_from_to): Likewise.
	* c-typeck.cc (c_omp_finish_iterators): Likewise.

gcc/cp/

	* parser.cc (cp_parser_omp_iterators): Use macros for accessing
	iterator elements.
	(cp_parser_omp_clause_affinity): Likewise.
	(cp_parser_omp_clause_depend): Likewise.
	(cp_parser_omp_clause_from_to): Likewise.
	(cp_parser_omp_clause_map): Likewise.
	* semantics.cc (cp_omp_finish_iterators): Likewise.

gcc/fortran/

	* trans-openmp.cc (gfc_trans_omp_array_section): Use macros for
	accessing iterator elements.
	(handle_iterator): Likewise.
	(gfc_trans_omp_clauses): Likewise.

gcc/

	* gimplify.cc (gimplify_omp_affinity): Use macros for accessing
	iterator elements.
	(compute_omp_iterator_count): Likewise.
	(build_omp_iterator_loop): Likewise.
	(remove_unused_omp_iterator_vars): Likewise.
	(build_omp_iterators_loops): Likewise.
	(enter_omp_iterator_loop_context_1): Likewise.
	(extract_base_bit_offset): Likewise.
	* omp-low.cc (lower_omp_map_iterator_expr): Likewise.
	(lower_omp_map_iterator_size): Likewise.
	(allocate_omp_iterator_elems): Likewise.
	(free_omp_iterator_elems): Likewise.
	* tree-inline.cc (copy_tree_body_r): Likewise.
	* tree-pretty-print.cc (dump_omp_iterators): Likewise.
	* tree.h (OMP_ITERATORS_VAR, OMP_ITERATORS_BEGIN, OMP_ITERATORS_END,
	OMP_ITERATORS_STEP, OMP_ITERATORS_ORIG_STEP, OMP_ITERATORS_BLOCK,
	OMP_ITERATORS_LABEL, OMP_ITERATORS_INDEX, OMP_ITERATORS_ELEMS,
	OMP_ITERATORS_COUNT, OMP_ITERATORS_EXPANDED_P): New macros.