Improve menu performance on N8x0

[Gerritv]

This patch addresses performance when displaying icons etc. using gui/internal. E.g the menus take a nooticeable time to draw and update. This is becuase the code tries to use svg re-scale which is only suported for svgt, and the images are all svg. The 3rd attempt is to use pre-scaled .png files. The patch moves pre-scaled .png to be first choice resulting in a crisp UI feel.

The same approach may apply to other GUI as well as to other devices. In fact since this change would not impact high speed devices, I recommend that this be in place for all platforms.

[Singesang]

Applied in r2006. Thanks Gerritv.