Consider annotating FF_API_ features in build.rs with version ranges

[FreezyLemon]

These FF_API_<FEATURE> flags come and go often, so the lists inside build.rs will keep growing. I think it makes sense to annotate these with the versions when they first and last appear in their respective version.h/version_major.h headers.

It would

• make it a lot easier to remove flags whenever support for old versions is dropped
• make it possible to see which flags are possible in the current version, so that downstream users know which FF_API features they can drop when upgrading FFmpeg version