* c-tree.h (enum c_typespec_kind, struct c_typespec,
	parser_xref_tag): New.
	(struct c_declspecs): Add tag_defined_p.  Adjust definition of
	typedef_p.
	(declspecs_add_type): Adjust prototypes.
	* c-parse.in (%union): Add tstype.
	(typespec_nonattr, typespec_attr, typespec_reserved_nonattr,
	typespec_reserved_attr, typespec_nonreserved_nonattr,
	structsp_attr, structsp_nonattr): Change to tstype.  Update
	actions.
	* c-decl.c (build_null_declspecs): Initialize tag_defined_p.
	(declspecs_add_type): Update to take struct c_typespec argument.
	Set tag_defined_p and typedef_p as appropriate.
	(xref_tag): Rename to parser_xref_tag and replace by wrapper.
	Update to return struct c_typespec.
	(shadow_tag_warned): Don't let empty declarations with qualifiers
	or storage class specifiers redeclare a tag if a previous
	declaration is visible.

testsuite:
	* gcc.dg/c99-tag-3.c, gcc.dg/declspec-14.c: New tests.

From-SVN: r89021