add time constraints and other checks on PC9x timestamp

add time constraints and other checks on PC9x timestamp

This involves making sure that the timestamp is within 15 mins of "now"
to be accepted. This has other rollover effects in that I don't send an
"old" C record on startup anymore, just send an A record followed by a K.
These days a newly minted C record will be along in 15mins or so anyway.

Made sh/newc terminal width aware.

Added CTY-1709 cty.dat data.