Use buffered fwrite(3) to build the udl Huffman table,
rather than doing 131074 write(2)s.
OK mglocker, deraadt.

Name fields in the udl_huffman struct same as on the driver side to
simplify reading.

Also avoid __packed struct to Huffman table in the driver side in favour
of performance. Instead generate the Huffman table with two ints.

Suggested, help and OK deraadt@

add error checking

if we do not use __packed, we must write the values more carefully
ok mglocker

16bit Huffman table for pixel difference compression on udl(4) devices.