allow new flow functions to be added to library overrides

[Secre-C]

No description provided.

[Sewer56]

I think this is fine?
Just make sure it doesn't bread existing mod setups because I don't quite 100% understand it.

[Secre-C]

This shouldn't affect current mod setups at all. The only thing that changed about existing functionality is that the search for an existing function index stops when that index is found, which would change behavior if there multiple functions of the same id within different modules in an unmodified instance of the script compiler (which there shouldn't be)

[Sewer56]

I'll make release when I get to PC