Prohibit C++ reference types in OpenACC regions

Prohibit C++ reference types in OpenACC regions

	gcc/
	* langhooks-def.h (lhd_omp_mappable_type): Add bool argument.
	* langhooks.c (lhd_omp_mappable_type): Likewise, for the
	parameter.
	* langhooks.h (struct lang_hooks_for_types): Add bool oacc
	argument.
	* gimplify.c (omp_notice_variable): Use it when calling the
	omp_mappable_type langhook.
	gcc/c/
	* c-decl.c (c_decl_attributes): Update call to omp_mappable_type.
	* c-typeck.c (c_finish_omp_clauses): Likewise.
	gcc/cp/
	* cp-tree.h (cp_omp_mappable_type): Add bool parameter.
	* decl2.c (cp_check_const_attributes): Likewise. Use it.
	(cp_omp_mappable_type): Update call to cp_omp_mappable_type.
	(cplus_decl_attributes): Likewise.
	* semantics.c (finish_omp_clauses): Likewise.
	gcc/testsuite/
	* g++.dg/goacc/reference.C: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gomp-4_0-branch@223179 138bc75d-0d04-0410-961f-82ee72b054a4