fixed scrollbar detection bug

Scrollbar size was only being returned when the
scrollbars were shown *and* you could scroll with them.
If they were shown, and you couldn't scroll (no where to
scroll to), then they were returning 0 size.

This is now fixed.
more work on implementing native cursors

Native cursors are working a little better.
Main improvements are on managing the
entering/leaving scrollbars, and switching
between url based cursors, and class based cursors.