Fixed bug where the air drag coefficient of a vehicle isn't updated when doors are opened/closed

[thorondir]

Summary

SUMMARY: Bugfixes "Updates vehicle drag when door opened/closed"

Purpose of change

When a vehicle's door is opened or closed, the drag doesn't appear to change when the vehicle is examined, even though drag is supposed to be different depending on whether doors and trunks are open. This causes vehicles to appear to have much higher drag when they are loaded with open doors/trunks which are subsequently closed.

Describe the solution

Set coeff_air_dirty=true at the end of the function vehicle::open_or_close(), so that vehicle::coeff_air_drag() performs a full calculation, instead of just returning coefficient_air_resistance.

Describe alternatives you've considered

I considered trying to find a more complicated solution, but decided against it, since this was a very simple solution to a fairly simple problem (and I would like to get some sleep) (this also seemed like the approach which would result in me having the least likelihood of screwing anything else up).

Testing

Recompiled game and summoned two identical vehicles. Closed all doors and trunks on both vehicles to find that they had different drag coefficients. Saved game and reloaded, after which the vehicles had the same drag coefficient. Opened doors and trunks, checked the vehicles, and found that the drag coefficients were unchanged.

Repeated this after the fix, and found that drag coefficients changed when expected to.

Additional context

Sorry if this is really scuffed. I've never done one of these before.