Fix sigwait namespace (bug 21550).

sigwait was added to POSIX in 1995; it is not in older POSIX versions
or XPG4 / XPG4.2.  Thus it should be declared only if
__USE_POSIX199506; signal.h wrongly declares it for __USE_POSIX.
(sigwaitinfo is correctly conditioned on __USE_POSIX199309.)  This
patch fixes the condition on the declaration of sigwait.

Tested for x86_64.  Because of other namespace problems this does not
allow any conform/ XFAILs to be removed.

	[BZ #21550]
	* signal/signal.h (sigwait): Only declare if [__USE_POSIX199506].

ChangeLog

@@ -1,3 +1,8 @@
+2017-06-12  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #21550]
+	* signal/signal.h (sigwait): Only declare if [__USE_POSIX199506].
+
 2017-06-12  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add

signal/signal.h

@@ -240,12 +240,14 @@ extern int sigaction (int __sig, const struct sigaction *__restrict __act,
 extern int sigpending (sigset_t *__set) __THROW __nonnull ((1));
 
 
+# ifdef __USE_POSIX199506
 /* Select any of pending signals from SET or wait for any to arrive.
 
    This function is a cancellation point and therefore not marked with
    __THROW.  */
 extern int sigwait (const sigset_t *__restrict __set, int *__restrict __sig)
      __nonnull ((1, 2));
+# endif /* Use POSIX 1995.  */
 
 # ifdef __USE_POSIX199309
 /* Select any of pending signals from SET and place information in INFO.