wmaker: Moved function prototype to the appropriate header

It is bad practice to define the prototype of an external function
inside a source file that wants to use it.

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

src/event.h

@@ -36,4 +36,7 @@ void ProcessPendingEvents(void);
 WMagicNumber wAddDeathHandler(pid_t pid, WDeathHandler *callback, void *cdata);
 Bool IsDoubleClick(WScreen *scr, XEvent *event);
 
+/* called from the signal handler */
+void NotifyDeadProcess(pid_t pid, unsigned char status);
+
 #endif /* WMEVENT_H */