conformtest: correct POSIX expectations for locale.h.

conformtest: correct POSIX expectations for locale.h.

When cleaning up conformtest expectations for POSIX for locale.h in
<https://sourceware.org/ml/libc-alpha/2012-11/msg00382.html>, I missed
that locale.h had contents defined in POSIX.2:1993 as well as
POSIX.1:1995/6.  Thus, LC_MESSAGES *should* in fact be required for
POSIX, because POSIX.2 says so; this patch adds that expectation
back.  Tested for x86_64.

	* conform/data/locale.h-data [POSIX] (LC_MESSAGES): Require.