Switch on FLAC support

[rossberg]

For some odd reason, upstream Raylib has FLAC support turned off by default. Could we switch it on for the OCaml package, analogous to JPEG?

Ideally, that should only require setting SUPPORT_FILEFORMAT_FLAC as a build option, though I am not sure what dependencies are involved.

[tjammer]

Raylib brings its dependencies, so that's no issue for us. I activated it by default in b5a603d. It increases the executables by around 100k, which is not too much on its own.
I still plan to properly modularize the bindings and then these option could really be optional. I don't think there is opam support (or even dune) for options, but we could choose them through environment variables or something.

[rossberg]

Wow, that was fast, thanks! Are you planning to make a new opam release anytime soon?

[tjammer]

I'm in the process of upgrading the bindings to dune 3 right now. Once this is done, I'll release to opam

[rossberg]

Splendid, thanks!