bugs
+ if train was abutting section boundary and is told to go,
+ maxinto is not updated properly, so if it is then
+ told to stop it stops owning the segment it may have
+ just entered
+ to reproduce: put shinkansen nose car at A6 (home location)
+ and nothing else. command speed 1 then speed 0
+ should now own X12 too but does not
+
+ on decel done, should replan train location to release future
+ segments no longer required
+ to reproduce: put shinkansen nose car at A6 (home location)
+ and nothing else. command speed 126 then 0
+
does not set serial port mode etc.
when checking future polarity possibility, does not account
for MARGIN_POLARISETIME - it just checks to see if