gdi32: Remove unused function.

[Huw Davies]

On Fri, Jul 08, 2016 at 03:58:04PM +0200, Sebastian Lackner wrote:
> I assume it was intentional to remove the is_in_rect() check from PtInRegion, but
> is it really such a good idea? For points outside of the extents rectangle it
> increased runtime from O(1) to O(log N), which could still matter in practice.

Good catch.  I hadn't meant to remove the extents test which is why I didn't
remove is_in_rect() in the original patch.

Thanks,
Huw.