SCUMM: Fix bug #6679 - INDY3 DOS-EGA: book of maps graphic glitch

Force correct width value for room 64 (book of maps) in Indy3. This
works around the wrong value stored in the data files of a specific
version of the game (DOS/EGA v1.0, according to scumm-md5.txt).
Merge pull request #527 from rrebello/bugfix-6679

SCUMM: Fix bug #6679 - INDY3 DOS-EGA: book of maps graphic glitch