Some code attempted to use `BIFIconID` instead of `int` to pass around
icon-ids. Problem is, that this is just a subset of the allowed ids,
more icons may be created at runtime and extend the range of valid
icon-ids. Such icons could give runtime warning prints.
Idea is to use a `using BIFIconID = int;` instead. This way there is
still a descriptive type name, while the whole dynamic range of possible
icon-ids is supported.
Additionally multiple `using BIFIconID = int;` declarations are valid,
so we can place these in multiple headers and use the type name in APIs
instead of just `int`, whithout having to include a single header
defining them. A type mismatch (one instance differs from the others)
will result in a compiler error.
Pull Request: https://projects.blender.org/blender/blender/pulls/111052
5dcf704324