include string.h for memset()

This avoids a warnings about implicit declaration of function 'memset'.

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Signed-off-by: Austin Foxley <austinf@cetoncorp.com>

libc/signal/sigset-cvt-mask.h

@@ -19,6 +19,8 @@
    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
    02111-1307 USA.  */
 
+#include <string.h>
+
 static __inline__ void __attribute__ ((unused))
 sigset_set_old_mask (sigset_t *set, int mask)
 {