Audio groupchats

[pranomostro]

Conference calls do not seem stable enough in the API yet:

/**
 * NOTE Compatibility with old toxav group calls. TODO(iphydf): remove
 */

But when this is sorted out, conference calls should be implemented asap.

[pranomostro]

Also: API change within ratox. Idea: prepend title of conference with 't ' (t space) or 'a ' (a space) for text and audio respectively?

[pranomostro]

Also: API change within ratox. Idea: prepend title of
conference with 't ' (t space) or 'a ' (a space) for text and audio
respectively?

Done.