Changes since 2.17:

o  Make timestamps in mkfs.com optional and add date stamper creation
o  Better cpm.5 documentation
o  Updated config.guess
o  Fixed error handling for corrupt images or diskdefs
o  Fixed off by one bug in fsck not detecting a wrong block number
o  Fixed too short directory buffer for directory sizes not matching
   whole blocks
o  Fixed default type of CP/M 3
o  Added description of -T to manuals
o  Added error check if reading the superblock fails
