Merge pull request #251 from x-qq/fix_scrollbar_segfaults

fix for scrollbar segfaults

* fixes #206
* fixes broken mousewheel scrolling of the scenedit palette
* removed boost threads dependency
* added foundation for further refactoring of the drawing and event handling code: interfaces and drawable manager with layering
* removed a bunch of unneeded redraw calls
* removed some repeated recalculation of effectively constant values (boe.actions)
* removed recalculation of effectively constant scrollbar and button positions (boe.graphics)

Closes #251

src/scenedit/scen.menus.mac.mm

@@ -164,13 +164,6 @@ void update_edit_menu() {
 	}
 }
 
-bool menuBarProcessEvent(const sf::Event&) {
-	return false;
-}
-
-void drawMenuBar() {
-}
-
 @implementation MenuHandler
 -(void) menuChoice:(id) sender {
 	handle_menu_choice(eMenu([[sender representedObject] intValue]));