WINTERMUTE: Introduce TransformTools
WINTERMUTE: Refactor some bits to use TransformStruct
WINTERMUTE: Bilinear scaling.

Refactor scale(), factor out actual mapping algorithm, add bilinear
scaling
WINTERMUTE: Add cast op Common::Rect => Rect32
WINTERMUTE: Add rotation

Add actual rotation code, make ticket-system transformStruct-aware
WINTERMUTE: Removed useless argument from rotate()
WINTERMUTE: Move if() outside transform loop
WINTERMUTE: Rename pixel copy functions
WINTERMUTE: Partial fix for mirrored sprites

Still weird with rotated + mirrored + scaled sprites. Offset.