New IFFDecoder

New IFF decoder that uses Graphics Decoder API.
Decodes ILBM and PBM images.

Changed gob, parallaction, queen and saga to use the new decoder.

gob has not been tested because I found no gob demo games to try it on.

parallaction has been tested with "Big Red Adventure" and "Nippon Safes" amiga demos.
queen has been tested with "Flight of the Amazon Queen" amiga demo.
saga has been tested with "Inherit the Earth" windows demo.

Moved PackBitsReadStream to common/iff_container

Removed old ILBM and PBM decoders.