Need signal.h for sigaction()

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/client.c b/client.c
index fd9727e..d883e65 100644
--- a/client.c
+++ b/client.c
@@ -12,6 +12,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <netdb.h>
+#include <signal.h>
 
 #include "fio.h"
 #include "server.h"