Expose object validation API?

[slouken]

It might be useful to be able to register object types and then use the API to validate pointers. I’m thinking specifically about SDL_ttf, but it might be handy in other cases.

Should we expose this in SDL 3.4? @libsdl-org/a-team, thoughts?

[slouken]

There are lots of other ways to handle this, so I'll close this for now.