Improve OpenMP map diagnostics.

Improve OpenMP map diagnostics.

2019-07-04  Andrew Stubbs  <ams@codesourcery.com>

	gcc/cp/
	* cp-tree.h (cp_omp_emit_unmappable_type_notes): New prototype.
	* decl.c (cp_finish_decl): Call cp_omp_emit_unmappable_type_notes.
	* decl2.c (cp_omp_mappable_type): Move contents to ...
	(cp_omp_mappable_type_1):  ... here and add note output.
	(cp_omp_emit_unmappable_type_notes): New function.
	* semantics.c (finish_omp_clauses): Call
	cp_omp_emit_unmappable_type_notes in four places.

	gcc/testsuite/
	* g++.dg/gomp/unmappable-1.C: New file.

From-SVN: r273078