- Optimized drawing code; now only items (sprites, text, screen masks) which have changed from the previous frame are redrawn, this speeds up things a lot
- Implemented dirty rectangles using a microtile array
- The previously committed Microtile Array implementation from SEL seemed buggy so I wrote my own version which works nicely so far (and is less code and GPL), only MicroTileArray::getRectangles uses parts from the old version, this will be changed later
- One known bug related to dirty rectangles remains: Sometimes the background isn't restored correctly and gfx artifacts are visible