vorbis-tools 1.4.3 fails to compile on Windows due to missing `convert_free_charset()`

[StephanTLavavej]

Reported upstream: https://gitlab.xiph.org/xiph/vorbis-tools/-/issues/2329

Fixed upstream: https://gitlab.xiph.org/xiph/vorbis-tools/-/commit/135b83184f39e57f99fcc2a5f2dd89045f6c74d0