ZScript interface to Trace() function

[jewalky]

Some things that were sacrificed in the process of exporting:

• actor flags filter (because actor flags work completely differently in ZScript)
• line flags filter (it doesn't make a lot of sense to have line flags, but no actor flags (but this can be returned back))
• fake/3D floor hit (because this structure is still not exported)

Added thing was HitTexture that now also works with walls, not just planes.
Callback function and results pointer were implemented as a virtual method + class field, as passing around structure and method pointers is not implemented properly.

Otherwise it's pretty complete reproduction of the original call.

Example code that uses it: https://hastebin.com/tefofehizu.cs
This example looks in player's view direction and returns the first relatively solid thing found. Doesn't try any advanced processing though.

[OrdinaryMagician]

My LineTrace submission can be rejected if this one gets in.

[jewalky]

Also, this is currently data-scope, since it's supposed to be purely informational.
By looking at the enums it seems calling Trace() can trigger stuff by simply tracing, so it might make sense to remove traceFlags or remove these flags if found. But here I'd need someone to tell me if it's true.

[coelckers]

I still have to think about whether to only use this or both submissions. This one is a lot more heavy duty so it may be of value to have a simpler alternative at your disposal. Feedback is welcome.

[MajorCooke]

I'd say having both would be nice. Modders can do more with more powerful stuff if they needed, or have a simpler alternative if they don't understand the bigger one.

[OrdinaryMagician]

Hmm, when you put it like that, it does make sense. I take back what I said then.