wmaker: Marked args as unused for compiler in WINGs Notif callback code

The mechanism of Notifications in the WINGs toolkit is relying on
callbacks to dispatch notifications, which means having a fixed argument
list for the handling function.

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

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

src/wmspec.c

@@ -1574,6 +1574,9 @@ static void wsobserver(void *self, WMNotification *notif)
 	WScreen *scr = (WScreen *) WMGetNotificationObject(notif);
 	const char *name = WMGetNotificationName(notif);
 
+	/* Parameter not used, but tell the compiler that it is ok */
+	(void) self;
+
 	if (strcmp(name, WMNWorkspaceCreated) == 0) {
 		updateWorkspaceCount(scr);
 		updateWorkspaceNames(scr);