* c-decl.c (shadow_tag_warned, grokdeclarator): Handle _Alignas

	* c-decl.c (shadow_tag_warned, grokdeclarator): Handle _Alignas
	specifiers.
	(build_null_declspecs): Initialize align_log and alignas_p fields.
	(declspecs_add_alignas): New.
	* c-parser.c (c_token_starts_declspecs): Handle RID_ALIGNAS.
	(c_parser_declspecs): Handle _Alignas specifiers.
	(c_parser_alignas_specifier): New.
	(c_parser_alignof_expression): Diagnose alignof use for non-C1X.
	Diagnose _Alignof (expression).
	* c-tree.h (struct c_declspecs): Add align_log and alignas_p
	fields.
	(declspecs_add_alignas): Declare.
	* ginclude/stddef.h (max_align_t): Define for C1X and C++11.
	* ginclude/stdalign.h: New.
	* Makefile.in (USER_H): Add stdalign.h.

c-family:
	* c-common.c (c_common_reswords): Add _Alignas and _Alignof.
	(c_sizeof_or_alignof_type): Diagnose alignof applied to a function
	type.
	(check_user_alignment): New.  Split out of
	handle_aligned_attribute.  Disallow integer constants with
	noninteger types.  Conditionally allow zero.
	(handle_aligned_attribute): Use check_user_alignment.
	* c-common.h (RID_ALIGNAS, check_user_alignment): New.

testsuite:
	* g++.dg/cpp0x/alignof3.C, gcc.dg/c1x-align-1.c,
	gcc.dg/c1x-align-2.c, gcc.dg/c1x-align-3.c, gcc.dg/c1x-align-4.c,
	gcc.dg/c90-align-1.c, gcc.dg/c99-align-1.c: New tests.
	* gcc.dg/gnu89-const-expr-1.c, gcc.dg/gnu90-const-expr-1.c,
	gcc.dg/gnu99-const-expr-1.c, gcc.dg/gnu99-static-1.c: Update
	expected diagnostics.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@181048 138bc75d-0d04-0410-961f-82ee72b054a4