Use uint64_t instead of ino_t

POSIX defines ino_t to be of an unsigned integer type, and searching
around the net didn't tell me of any definitions conflicting that. So
every ino_t can be represented in an uint64_t. (Assuming that is the
largest integer type in use for an inode number, but I'm sure that
assumption will hold for a while)

(dev_t, on the other hand, is a bit messier. Still figuring out what to
do with that.)