Export FBoundingBox to ZScript.

[Doom2fan]

https://forum.zdoom.org/viewtopic.php?f=15&p=1082433

[coelckers]

Looking at this, I see two immediate issues:

1. Having access functions to single variables because the internal fields are badly named is not good. Most of the exported methods are mere setters and getters.
   Better export it in a way that the fields can be used directly, especially for a pure data class like this one.

2. If you export a data class as an object it needs to be serializable.

[Doom2fan]

All the getters and setters are the same as FBoundingBox's. m_Box cannot be exported (At least as far as I know), as it's a protected variable, not public.
If you want me to, however, I can merge the individual getters into a single "Get" function.

That said, I'd like to know if there's any way to export FBoundingBox itself - I had to create a new class named "DBoundingBox", as FBoundingBox doesn't inherit from DObject, and making it inherit from DObject causes problems, as GZDoom's code frees it manually currently.

[Doom2fan]

I can't seem to get it to serialize correctly - whenever I load a save m_Box's values are wrong, so I'm honestly just gonna give up on this.

This all feels like the wrong way to do this - the actual FBoundingBox class should be exported, and all the places where GZDoom allocates/creates or frees it manually should be changed - That way it'd have more uses instead of pretty much being only being useful for mods.