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.

ChangeLog

@@ -1,5 +1,7 @@
 2015-05-20  Joseph Myers  <joseph@codesourcery.com>
 
+	* conform/data/locale.h-data [POSIX] (LC_MESSAGES): Require.
+
 	* conform/data/unistd.h-data (_POSIX_VERSION): Require.
 	(_POSIX2_C_VERSION): Require if [POSIX || XPG3 || XPG4 || UNIX98].
 	Do not mention otherwise.

conform/data/locale.h-data

@@ -31,7 +31,7 @@ macro-constant NULL == 0
 macro-int-constant LC_ALL
 macro-int-constant LC_COLLATE
 macro-int-constant LC_CTYPE
-#if !defined ISO && !defined ISO99 && !defined ISO11 && !defined POSIX
+#if !defined ISO && !defined ISO99 && !defined ISO11
 macro-int-constant LC_MESSAGES
 #endif
 macro-int-constant LC_MONETARY