[BZ #22244] Fix yn(n,0) without SVID wrapper

Without SVID compat wrapper yn(n,0) and ynf(n,0) does not raise
the divide-by-zero excpetion and it may return inf with the wrong
sign for n < 0.

	[BZ #22244]
	* sysdeps/ieee754/dbl-64/e_jn.c (__ieee754_yn): Fix x == 0 case.
	* sysdeps/ieee754/flt-32/e_jnf.c (__ieee754_ynf): Likewise.