remove the old sound api

Remove all traces of the old sound api from pidgin

Remove all traces of the old sound api from finch

Remove all references to the old sound api from libpurple

Remove the old sound files

Update ChangeLog.API for all the removals

Testing Done:

Compile tested finch. Ran pidgin, verified the preferences window works, the pounce window dies on something talkatu related but that will be addressed separately.

Reviewed at https://reviews.imfreedom.org/r/58/