Enabling moving window in cycles.

WindowMaker have a Maximus feature expanded by ability to resize windows
to half screen (horizontally and vertically). Although, there was no way
to move windows between different heads (while screen is spanned between
different monitors - heads - if there was no xinerama used). This patch
enables possibility for moving windows between states. Assuming we have
a window on first head, maximize left would make the window occupy left
half of the screen. Assuming we have another head right of the first
head, following scenario will be possible:

- maximize right will make window occupy entire free space (just like
  ordinary maximizing will do)
- another maximize right will make window be maximized half right of the
  first screen
- another maximize right will make window be maximized half left on
  second screen
- another maximize right will make window be maximized on second screen
- another maximize right will make window be maximized half right on
  second screen
- another maximize right will make no effect

So it will cycle between half screen/fullscreen making window to travel
from left to right. Same goes for opposite direction.

src/actions.h

@@ -57,7 +57,7 @@ void wSelectWindows(WScreen *scr, XEvent *ev);
 void wSelectWindow(WWindow *wwin, Bool flag);
 void wUnselectWindows(WScreen *scr);
 
-void wMaximizeWindow(WWindow *wwin, int directions);
+void wMaximizeWindow(WWindow *wwin, int directions, int head);
 void wUnmaximizeWindow(WWindow *wwin);
 void handleMaximize(WWindow *wwin, int directions);