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/game/boe.menus.hpp

@@ -22,12 +22,6 @@ void menu_activate();
 void hideMenuBar();
 void showMenuBar();
 
-// If a menubar runs inside our own event loop, we need ways to supply it with events and to draw it.
-namespace sf { class Event; };
-// Return true if event has been consumed by the menubar.
-bool menuBarProcessEvent(const sf::Event&);
-void drawMenuBar();
-
 enum class eMenu {
 	NONE, ABOUT, PREFS, QUIT,
 	FILE_NEW, FILE_OPEN, FILE_ABORT, FILE_SAVE, FILE_SAVE_AS,