* builtins.def [DEF_GCC_BUILTIN]: Require an explicit ATTRS
	argument.  Mark BUILT_IN_RETURN, BUILT_IN_EH_RETURN,
	BUILT_IN_LONGJMP and BUILT_IN_TRAP as noreturn, the ISO C99
	floating point unordered comparisons (e.g. __builtin_isgreater)
	as const, and leave the remaining GCC_BUILTINs unchanged.

	* c-decl.c (builtin_function): No need to explicitly mark
	BUILT_IN_RETURN and BUILT_IN_EH_RETURN as noreturn.

	* cp/decl.c (builtin_function_1): No need to explicitly mark
	BUILT_IN_RETURN and BUILT_IN_EH_RETURN as noreturn.

From-SVN: r55805