inodes - using types with known size

inodes - using types with known size

- fixes a problem in inodes truct definitions. The original definitions use
  posix types. These types don't have well defined size. Therefore when
  compiling mkfs on a different system natively the inodes sizes do not match.
  This patch replaces the posix types with interger types of the same size and
  signedness as the original types in use.