Fix XPG4 bsd_signal namespace (bug 21552)

[Joseph Myers]

bsd_signal was added in XPG4.2, so should be declared for
__USE_XOPEN_EXTENDED, instead of the present __USE_XOPEN condition.
This patch fixes the condition accordingly.

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

2017-06-05  Joseph Myers  <joseph@codesourcery.com>

	[BZ #21552]
	* signal/signal.h (bsd_signal): Declare if [__USE_XOPEN_EXTENDED],
	not [__USE_XOPEN].

diff --git a/signal/signal.h b/signal/signal.h
index b311473..8a140d4 100644
--- a/signal/signal.h
+++ b/signal/signal.h
@@ -94,7 +94,7 @@ extern __sighandler_t __REDIRECT_NTH (signal,
 # endif
 #endif
 
-#if defined __USE_XOPEN && !defined __USE_XOPEN2K8
+#if defined __USE_XOPEN_EXTENDED && !defined __USE_XOPEN2K8
 /* The X/Open definition of `signal' conflicts with the BSD version.
    So they defined another function `bsd_signal'.  */
 extern __sighandler_t bsd_signal (int __sig, __sighandler_t __handler)

-- 
Joseph S. Myers
joseph@codesourcery.com