trek(6): Drop fast/slow modes and the broken autodetection

trek(6): Drop fast/slow modes and the broken autodetection

These modes were not documented in the manpage, the autodetect
logic was reversed (only terminals with baud < 1200 would get the fast
flag) and even the source was confused claiming this fast setting was
for terminals with baud > 300.

The only thing that changes is the automatic short range scan output
down when entering a new sector. Now the full report is shown always
but can still be somewhat customized.

Incidentally, this also obviates the need for termios. yay!

Submitted-by:  Ulrich Spoerlein <uqs@spoerlein.net>
Dragonfly-bug: <http://bugs.dragonflybsd.org/issue1470>