Rescale smileys smoothly, fix #501
Fix leak, enable NRVO in Core::getUsername
Fix uninitialized return value in createVpxImage
Handle toxcore failures in Core::onAvMediaChange

No, I'm not above using goto for centralized error handling.
Fix leak, enable NRVO in Core::getStatusMessage
Add some core doc comments, remove dead code
Fix small memory leaks

Mostly to make valgrind happy
Made Mute speakers button work
Merge branch 'pr553'