[Added] DamageMobj DMG_NO_PAIN Flag

[Major Cooke]

Pull Request

Simplifies the desire to switch off pain effects entirely so entities don't have to waste time flipping a flag on and then turning it back off again, and could prove useful later if internal functions need them. Plus, I'm not sure if DamageMobj even has time to properly check if the thing is still painless when it starts.

[Rachael]

I submitted some change requests.

Also let's not begin a pull request barrage, again, please?

[Rachael]

This is going to need a lot of testing, because DamageMobj is a function that gets called quite a lot internally for lots of different reasons. The only way I can be confident in this code is if it's tested "in the wild", so I am going to go ahead and do a QZDoom merge of this and let it stay pending until some people have picked it up.

[Graf Zahl]

I still regret accepting all the pain mess - this only makes it worse.

[Major Cooke]

That's why I made this as simple as possible, because I can rely on making my own variant of pain chancing via the virtual override. I'm letting DamageMobj do its work on the inside without causing any pain just so I can get some numbers from damagefactor modifications and then getting the number immediately.

I have absolutely no intention of introducing a DMG_CAUSE_PAIN or DMG_ALLOW_PAIN flag at all.

[Major Cooke]

Close me. This was added.