c-family:
	* c-common.c (c_common_reswords): Add _Thread_local.

c:
	* c-tree.h (struct c_declspecs): Add thread_gnu_p field.
	* c-parser.c (c_parser_declspecs): Mention _Thread_local in
	comment.
	* c-decl.c (shadow_tag_warned, grokdeclarator): Mention __thread
	or _Thread_local as appropriate in diagnostics.
	(build_null_declspecs): Initialize ret->thread_gnu_p.
	(declspecs_add_scspec): Handle either __thread or _Thread_local
	for RID_THREAD.  Diagnose _Thread_local for pre-C11 standards if
	pedantic.  Do not disallow _Thread_local extern and _Thread_local
	static.

testsuite:
	* gcc.dg/c90-thread-local-1.c, gcc.dg/c99-thread-local-1.c,
	gcc.dg/c11-thread-local-1.c, gcc.dg/c11-thread-local-2.c: New
	tests.
	* gcc.dg/tls/diag-2.c, objc.dg/tls/diag-2.m: Update expected
	diagnostics.

From-SVN: r204711