Replace signal by sigaction

Changelog

@@ -2,6 +2,7 @@
 	Removed features:
 		- Remove (broken) hmode
 		- Old style key binding and mode launcher.
+		- Old TIMING code.
 	New features:
 		- Word movement in entry box. (#126)
 		- PID file to avoid duplicate Rofi.

source/rofi.c

@@ -1715,7 +1715,10 @@ int main ( int argc, char *argv[] )
     }
 
     // Set up X interaction.
-    signal ( SIGCHLD, catch_exit );
+    const struct sigaction sigchld_action = {
+        .sa_handler = catch_exit
+    };
+    sigaction ( SIGCHLD, &sigchld_action, NULL );
 
     x11_setup ( display );