COMMON: Add PackBitsReadStream to iff_container
GRAPHICS: New IFFDecoder that decodes ILBM and PBM images
GOB: Update to new IFFDecoder for ILBM images
PARALLACTION: Update to new IFFDecoder for ILBM images
QUEEN: Update to new IFFDecoder for ILBM images
SAGA: Update to new IFFDecoder for PBM images
GRAPHICS: Delete iff.cpp and iff.h since all ILBM and PBM decoding is handled by IFFDecoder now