PR c/66970 - Add __has_builtin() macro

PR c/66970 - Add __has_builtin() macro

gcc/ChangeLog:

	PR c/66970
	* doc/cpp.texi (__has_builtin): Document.
	* doc/extend.texi (__builtin_frob_return_addr): Correct spelling.

gcc/c/ChangeLog:

	PR c/66970
	* c-decl.c (names_builtin_p): Define a new function.

gcc/c-family/ChangeLog:

	PR c/66970
	* c-common.c (c_common_nodes_and_builtins): Call c_define_builtins
	even when only preprocessing.
	* c-common.h (names_builtin_p): Declare new function.
	* c-lex.c (init_c_lex): Set has_builtin.
	(c_common_has_builtin): Define a new function.
	* c-ppoutput.c (init_pp_output): Set has_builtin.

gcc/cp/ChangeLog:

	PR c/66970
	* cp-objcp-common.c (names_builtin_p): Define new function.

gcc/testsuite/ChangeLog:

	PR c/66970
	* c-c++-common/cpp/has-builtin-2.c: New test.
	* c-c++-common/cpp/has-builtin-3.c: New test.
	* c-c++-common/cpp/has-builtin.c: New test.

From-SVN: r277544