New option for enabling alternative half-maximized window movement.

Added new option to Window Maker for enabling alternative way for
half-maximized windows movement. Option can be found on Expert section
in WPrefs app.

src/WindowMaker.h

@@ -366,6 +366,7 @@ extern struct WPreferences {
 	char snap_to_top_maximizes_fullscreen;
 	char drag_maximized_window;        /* behavior when a maximized window is dragged */
 	char move_half_max_between_heads;  /* move half maximized window between available heads */
+	char alt_half_maximize;            /* alternative half-maximize feature behavior */
 
 	char highlight_active_app;         /* show the focused app by highlighting its icon */
 	char auto_arrange_icons;           /* automagically arrange icons */