Disable system DPI scaling on Windows.

We scale the video just fine (or rather, better)
ourselves.
The GUI might be in trouble here though, since it
does not want its video to be scaled by the OS but
it also isn't DPI aware either...


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@37154 b3059339-0415-0410-9bf9-f77b7e298cf2