Reapply patch from http://issuetracker.delphi-jedi.org/view.php?id=5996
Fix an obscure bug with hidden scroll bars.
If the zoom percentage is set so high that a horizontal scroll bar would be shown, but the horizontal scroll bar is hidden, then clicking the down button on the vertical scroll bar does nothing.  Observed on my Windows 7 machine.  This may be a bug in Windows; a workaround is to hide the scrollbar after configuring it instead of before.
Merge pull request #4 from joshkel/preview-enhancements

Preview enhancements