binary addons: replace prebuilt dependencies with proper builds

This replaces all the prebuilt dependencies (libmp3lame, libogg, libvorbis and libflac) of the audioencoder binary addons used in the win32 buildsystem with proper builds i.e. every dependency is built by downloading a tarball from our mirrors and then building it. It doesn't touch the generic cmake buildsystem for binary addons at all but only the win32 specific dependency buildsystem.

I have verified that all audioencoders are still working on win32.

This needs an adjustment in audioencoder.vorbis which needs to be PRed and merged before this. Once we have agreed to merge this I will PR the change to audioencoder.vorbis, merge it and then update this PR.