Made mkfs a little smarter about how to report empty devices.
Made mkfs a little smarter about how to report empty devices.

Also a little smarter about manually specified number of blocks that is
larger than the device capacity.


danielbarter/minix_book,danielbarter/minix_book,veritas-shine/minix3-rpi,danielbarter/minix_book,veritas-shine/minix3-rpi,danielbarter/minix_book,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,danielbarter/minix_book,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi,danielbarter/minix_book,veritas-shine/minix3-rpi,veritas-shine/minix3-rpi