Update tpo.cc (#643)

Update tpo.cc (#643)

Some .tpo file tracks were/are parsed such that wild jumps occur in lat/lon, creating invalid coords which were not caught by output routines. Some logic flaws and int size errors have been fixed, but some tracks still contain invalid points. Tracks not corrected by this patch now result in warning messages to STDOUT. Entirely valid tracks will also generate warnings if lat or lon changes by a full degree between adjacent track points (should never happen). Non-fatal warning allows manual removal of the few bad track points  in an output format like GPX. Damage is apparently limited to half a dozen incremental points before the next full point, but that can't be guaranteed.

Co-authored-by: tsteven4 <13596209+tsteven4@users.noreply.github.com>