Support expansion of reserved locations wrapped in virtual locations

Support expansion of reserved locations wrapped in virtual locations

libcpp/

	* include/line-map.h (linemap_expand_location): Take a line table
	parameter.  Update comment.
	(linemap_resolve_location): Update comment.
	(linemap_expand_location_full): Remove.
	* line-map.c (linemap_resolve_location):  Handle reserved
	locations; return a NULL map in those cases.
	(linemap_expand_location): If location is reserved, return a
	zeroed expanded location.  Update comment.  Take a line table to
	assert that the function takes non-virtual locations only.
	(linemap_expand_location_full): remove.
	(linemap_dump_location): Handle the fact that
	linemap_resolve_location can return NULL line maps when the
	location resolves to a reserved location.

gcc/
	* input.c (expand_location): Rewrite using
	linemap_resolve_location and linemap_expand_location.  Add a
	comment.

From-SVN: r180426