An API for lazy builtin macros.

An API for lazy builtin macros.

	libcpp/
	* include/libcpp.h (struct cpp_callbacks): Adjust
	user_builtin_macro callback.
	(cpp_define_lazily, cpp_define_lazy): Declare.
	* macro.c (enter_macro_context, warn_of_redefinition): Adjust.
	(cpp_define_lazily, cpp_define_lazy): Define.
	(cpp_macro_definition): Adjust.
	* pch.c (write_macrdef, save_macros): Likewise.
	* directives.c (do_ifdef, do_ifndef): Adjust.
	* expr.c (parse_defined): Likewise.
	gcc/c-family/
	* c-cppbuiltin.c (lazy_hex_fp_value): Adjust for API changes.
	(builtin_define_with_hex_fp_valye): Likewise.

From-SVN: r263297