bench.c: Include signal.h, not non-std sys/signal.h

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

bench.c

@@ -44,11 +44,11 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/resource.h>
-#include <sys/signal.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/time.h>