(to_oct): Now static. Value arg is now uintmax_t. Accept new args

(to_oct): Now static.  Value arg is now uintmax_t.  Accept new args
giving name of type of octal field, for error messages.  Report an
error if the value is too large to fit in the field.
(gid_to_oct, major_to_oct, minor_to_oct, mode_to_oct, off_to_oct,
size_to_oct, time_to_oct, uid_to_oct, uintmax_to_oct): New functions.

(write_eot, write_long, finish_header, deal_with_sparse,
finish_sparse_file, dump_file): Use dev_t, off_t, ssize_t, size_t when
appropriate.  Remove now-useless casts.  Use unsigned long to print
*_t types, except use STRINGIFY_BIGINT for off_t.

(find_new_file_size): 1st arg is now off_t*.
(finish_sparse_file): Args now use off_t, not long.
Check for lseek error.
(create_archive, dump_file): Cast -1 to dev_t when necessary.
(dump_file): Device arg is now dev_t.
Avoid overflow when testing whether file has holes
by using the new ST_NBLOCKSIZE macro.