wNETWMCheckClientHintChange should be void

wNETWMCheckClientHintChange should be void

The function wNETWMCheckClientHintChange returns a Bool,
but this value is never used, son can be removed.

This function now is void.

kix@osaka:~/src/wmaker/wmaker-crm-tosnd/src$ grep wNETWMCheckClientHintChange *.[ch]
client.c:                       wNETWMCheckClientHintChange(wwin, event);
wmspec.c:Bool wNETWMCheckClientHintChange(WWindow * wwin, XPropertyEvent * event)
wmspec.h:Bool wNETWMCheckClientHintChange(WWindow *wwin, XPropertyEvent *event);