compressor bugfix - again

the previous fix didn't really fix every condition, I hope this does
also, the stm_decomp tool has been added, to be able to decompress an stm blob into uncompressed binary data and outputting a text description of the compressed data

compressor bugfix

the compressor could silently fail with some very specific sequences of values, leading to wrong compressed data - this has been fixed now

improved format and ASM decompressor

(image width stored in data file, ASM decompressor is now IRQ and VRAM
*safe*
- also: official name is now "ShrunkTileMap")

fixed carry in incremental runs #2

hopefully true this time :|