CHANGE: Take into account if a convoy is behind its estimated arrival time when judging which convoy to board by assuming that it will be just as much late again as it already is.
FIX: Possible loading/saving anomalies with older saved games in some cases.
REVERT: Passengers/mail/goods no longer refuse to board a convoy waiting for spacing until shortly before departure: this is no longer necessary with the estimated departure/arrival times system.