builtins.def (BUILT_IN_NEXTAFTER, [...]): Use ATTR_MATHFN_ERRNO instead of ATTR_MATHFN_FPROUNDING_ERRNO.

	* builtins.def (BUILT_IN_NEXTAFTER, BUILT_IN_NEXTAFTERF,
	BUILT_IN_NEXTAFTERL, BUILT_IN_NEXTTOWARD, BUILT_IN_NEXTTOWARDF,
	BUILT_IN_NEXTTOWARDL): Use ATTR_MATHFN_ERRNO instead of
	ATTR_MATHFN_FPROUNDING_ERRNO.

From-SVN: r255586