Add VehicleMission::MissionType::RestartNextMission enum serialization
Add VehicleMission::MissionType::RestartNextMission enum serialization

This was missing from the serialization generation source, so any saves that
happened to contain missions of this type would fail

pmprog/OpenApoc,steveschnepp/OpenApoc,steveschnepp/OpenApoc,Istrebitel/OpenApoc,pmprog/OpenApoc,Istrebitel/OpenApoc