Fix a typo.

http://bugs.gentoo.org/show_bug.cgi?id=88546

--- configure
+++ configure
@@ -20231,7 +20231,7 @@
   # See if we find them without any special options.
   # Don't add to $LIBS permanently.
   ac_save_LIBS=$LIBS
-  LIBS="-lX $LIBS"
+  LIBS="-lX11 $LIBS"
   cat >conftest.$ac_ext <<_ACEOF
 /* confdefs.h.  */
 _ACEOF