* c-decl.c (shadow_tag_warned): Check for _Noreturn.
	(quals_from_declspecs): Assert _Noreturn not present.
	(grokdeclarator): Handle _Noreturn.
	(build_null_declspecs): Initialize noreturn_p.
	(declspecs_add_scspec): Handle RID_NORETURN.
	* c-parser.c (c_token_starts_declspecs, c_parser_declspecs)
	(c_parser_attributes): Handle RID_NORETURN.
	* c-tree.h (struct c_declspecs): Add noreturn_p.
	* ginclude/stdnoreturn.h: New.
	* Makefile.in (USER_H): Add stdnoreturn.h.

c-family:
	* c-common.c (c_common_reswords): Add _Noreturn.
	(keyword_is_function_specifier): Handle RID_NORETURN.
	* c-common.h (RID_NORETURN): New.

testsuite:
	* gcc.dg/c1x-noreturn-1.c, gcc.dg/c1x-noreturn-2.c,
	gcc.dg/c1x-noreturn-3.c, gcc.dg/c1x-noreturn-4.c,
	gcc.dg/c1x-noreturn-5.c: New tests.

From-SVN: r177881