Fix ldbl-128 rintl/nearbyintl just like flt-32 variants.

	* sysdeps/ieee754/ldbl-128/s_nearbyintl.c (__nearbyintl): Do not
	manipulate bits before adding and subtracting TWO112[sx].
	* sysdeps/ieee754/ldbl-128/s_rintl.c (__rintl): Likewise.

(cherry-picked from commit a78bc654)