Fortran/OpenMP: Middle-end support for mapping of DT with allocatable components

gcc/ChangeLog:

	* langhooks-def.h (lhd_omp_deep_mapping_p,
	lhd_omp_deep_mapping_cnt, lhd_omp_deep_mapping): New.
	(LANG_HOOKS_OMP_DEEP_MAPPING_P, LANG_HOOKS_OMP_DEEP_MAPPING_CNT,
	LANG_HOOKS_OMP_DEEP_MAPPING): Define.
	(LANG_HOOKS_DECLS): Use it.
	* langhooks.cc (lhd_omp_deep_mapping_p, lhd_omp_deep_mapping_cnt,
	lhd_omp_deep_mapping): New stubs.
	* langhooks.h (struct lang_hooks_for_decls): Add new hooks
	* omp-expand.cc (expand_omp_target): Handle dynamic-size
	addr/sizes/kinds arrays.
	* omp-low.cc (build_sender_ref, fixup_child_record_type,
	scan_sharing_clauses, lower_omp_target): Update to handle
	new hooks and dynamic-size addr/sizes/kinds arrays.