BZ#16469: don't drop trailing dot in res_nquerydomain(..., name, NULL, ...)

If we drop it here, we will fail to detect a duplicate trailing dot
later on.  Retaining, OTOH, has no ill effects whatsoever, and it even
saves us the trouble of copying the domain name minus the trailing
dot, like we used to do.

for ChangeLog

	[BZ #16469]
	* NEWS: Update.
	* resolv/res_query.c (__libc_res_nquerydomain): Retain
	trailing dot.
	* posix/tst-getaddrinfo5.c: New.
	* posix/Makefile (tests): Add it.