Need signal.h for sigaction()

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/server.c b/server.c
index 4c12f65..0b1c27f 100644
--- a/server.c
+++ b/server.c
@@ -13,6 +13,7 @@
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <syslog.h>
+#include <signal.h>
 
 #include "fio.h"
 #include "server.h"