params window id issue

The AntTweakBar window id of the bars is not connected to the window, but gradually increased instead. This causes an issue that a bar cannot be dragged above an other bar, because the second bar steals the focus. The issue is illustrated in the following video:
http://youtu.be/23hYreixDjs
I attempted to fix this by connecting the window id to the window pointer. There is a seemingly unrelated issue that the font of the bars gets mixed up when the font size is changed, which also seems to be fixed by this modification.