UltraRogue: don't swap signal handlers.

In md_shellescape(), signal handlers for SIGINT and SIGQUIT were saved
and restored, but exchanged in the process.  This was fixed in the
other games by commit 600873555ec0.

Deleting md_shellescape() might have been a better fix.  It is
apparently unused.

urogue/mdport.c

@@ -397,9 +397,9 @@ md_shellescape()
         while (wait(&ret_status) != pid)
             continue;
 	    
-        signal(SIGINT, myquit);
+        signal(SIGINT, myend);
 #ifdef SIGQUIT
-        signal(SIGQUIT, myend);
+        signal(SIGQUIT, myquit);
 #endif
     }