Remove warnings

* Remove assigned but not used variables (GCC 4.6)
* Bump _XOPEN_SOURCE to 600, ridding of FreeBSD warnings (this probably need
  to be tweaked on a per-implementation basis as problems arise)

util/wmmenugen.c

@@ -18,12 +18,6 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#if __GLIBC__ && \
-    (_XOPEN_SOURCE && _XOPEN_SOURCE < 500) || \
-    !_XOPEN_SOURCE
-#define _XOPEN_SOURCE 500		/* nftw */
-#endif
-
 #include <sys/types.h>
 #include <sys/stat.h>