Theming Support

[Mike Hearn]

For those who want another screenshot:

  http://plan99.net/~mike/files/winecfg-reluna.png

As you can see there are still quite a few visual glitches. The tab
control or property sheet API doesn't seem to set the embedded window to
the right theme/position, though I've seen similar artifacts on the real
Windows XP so maybe we can't fix that. 

There's a fixme about image loading. Frank, you can get Reluna.msstyles
from here:

 http://plan99.net/~mike/files/Reluna.msstyles

Also buttons and combo boxes aren't themed yet, it seems.

thanks -mike