Forces vehicle::of_turn to zero upon load rather than leaving it
undefined.

Normally this doesn't matter because vehicle::gain_moves() will
clobber it when the map next updates all the vehicles. However, if the
player is driving really fast it's possible for a vehicle to be loaded
while the map is in the middle of updating the vehicles, where the
undefined of_turn was sometimes an issue.
Get the pseudo ordering by optionnames back.
Fix UI menu auto-hotkey assignment:

prevent lag by the loop when all possible hotkeys have been used up.
Use uimenu::addentry with a std::string as last parameter, not a const char*, as that would invoke the printf formatting.
Merge remote-tracking branches 'dda/pr/7823', 'dda/pr/7831' and 'dda/pr/7835' into dda-master

* dda/pr/7823:
  Forces vehicle::of_turn to zero upon load rather than leaving it undefined.

* dda/pr/7831:
  Get the pseudo ordering by optionnames back.

* dda/pr/7835:
  Fix UI menu auto-hotkey assignment: