Remove some window manager optimizations to account for Basic and Classic theme rendering

As I should have expected, Windows handles window redraws very
differently under non-Aero themes.  I've written the window manager to
try and minimize forced redraws, and under Aero this gives great
results, but under Win 7 Basic or Classic themes, strange and horrible
things are happening.  (e.g. try moving the main window prior to this
commit!)

This quick fix alleviates the bulk of the problems, but I'll need to do
extra testing to make sure I haven't missed other problems.