flexfax: Retrain Negative in Class 1 (was: HylaFax does not stop sending pages)

[David Woolley <david@djwhome.demon.co.uk>]

> Aug 06 20:11:20.49: [30427]: -->
> [54:]

0000000   [   5   4   : 023 021 023 021 023 021 023 021 023 021 023 021
0000020 023 021 023 021 023 021 023 021 023 021 023 021 023 021 023 021
*
0000060 023 021 023 021 023 021 023 021 023 021   ]  \n
0000074

The modem is trying software flow control, but the computer is ignoring
it.  If it also uses hardware flow control, this might not be a problem,
but otherwise it would cause the remote system to reject the transmission
in this way.

> Aug 06 20:11:23.11: [30427]: SEND recv RTN (retrain negative)

The remote system requested that the line be re-calibrated and the page
re-sent.  This can sometimes be caused by coding errors and there is a
patch to correct incorrect fax coding in the tag line.  It can also be
caused by line quality problems (the real intention of this condition)
and there is a patch to retry at lower speeds.