Fix up some printflike attributes.

control.c

@@ -386,7 +386,7 @@ control_pause_pane(struct client *c, struct window_pane *wp)
 }
 
 /* Write a line. */
-static void
+static void printflike(2, 0)
 control_vwrite(struct client *c, const char *fmt, va_list ap)
 {
 	struct control_state	*cs = c->control_state;