Use an enum class to prevent implicit conversion between trigger
behavior flags and other integers. Fix up various resulting breaks,
which look like bugs:
- Descent 2 editor mode could modify trigger::flags, but used
TRIGGER_FLAG_* values, which specify the actions for a Descent 1
trigger when it executes, not the behavior properties for a trigger.
- Adding a trigger set its flags to 0, then cleared all flags except
TRIGGER_ON. Since the flags were just set to 0, the mask operation is
useless. Remove it.
- trigger_turn_all_ON cleared all flags except TRIGGER_ON. This seems
to be completely wrong. Change it to remove
trigger_behavior_flags::disabled. Descent 1 has no (working) support
for disabling triggers, so make trigger_turn_all_ON exclusive to
Descent 2.
- wall_restore_all would enable TRIGGER_ON in both games. Descent 1
never reads TRIGGER_ON. Descent 2 uses this field for trigger
behavior flags, and TRIGGER_ON is not a behavior flag.
- For Descent 1 builds, remove the modification of the field.
- For Descent 2 builds, change it to clear
trigger_behavior_flags::disabled.
Replace calls to window_close(Game_wind) with returning window_event_result::close to game handler. Applies to when DoEndGame() is called, DoGameOver() is called, aborting in the kmatrix screen (multiplayer game) during AdvanceLevel() and playing one demo frame causes playback to stop in GameProcessFrame(). Closing a window within its handler is problematic - it can result in an unstable state.
The declaration of valptridx_specialized_types needed to be found by
Argument Dependent Lookup, but this was inconvenient for some types.
Split the declaration of valptridx_specialized_types out from the
definition of valptridx global subtype.
