(allocated_size): Now size_t, and now initialized to 0.

(allocated_size): Now size_t, and now initialized to 0.
(prepare_record_buffer): Arg is now size_t.
Remove now-useless casts.

(main): Use `long' for status, so that it can store ssize_t.
Use daddr_t, mode_t, size_t, off_t when appropriate.
Convert daddr_t and off_t values ourselves, since they might be longer
than long.  Convert other types using `long' primitives.
When processing MTIOCTOP, do not try to pass resulting
count back, since it won't work (it could be too large) and it's
not expected anyway.