WPrefs: Marked args as unused for compiler in signal handlers

When the process receive a signal, a callback function is used, which
means having a fixed argument list for that application function.

It is then correct to not use the argument, so this patch adds the
appropriate stuff to avoid a false report from compiler.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>

WPrefs.app/main.c

@@ -45,6 +45,9 @@ static int DeadChildrenCount = 0;
 
 static void wAbort(Bool foo)
 {
+	/* Parameter not used, but tell the compiler that it is ok */
+	(void) foo;
+
 	exit(1);
 }