(svn r7094) -Codechange: Get rid of the window-specific code in DoZoomInOutWindow (enable, disable

buttons depending on calling window, game-mode); handle it by broadcasting messages
 to the calling window, because that knows how and what buttons to set.

viewport.h

@@ -31,6 +31,7 @@ enum {
 bool DoZoomInOutWindow(int how, Window *w);
 void ZoomInOrOutToCursorWindow(bool in, Window * w);
 Point GetTileZoomCenterWindow(bool in, Window * w);
+void HandleZoomMessage(Window *w, const ViewPort *vp, byte widget_zoom_in, byte widget_zoom_out);
 
 void OffsetGroundSprite(int x, int y);