Support for variable sized g729 frames

[rajatsrao]

The g729 standard actually allows the frame size to be 10, 20, 30, 40, 50 or 60 bytes, with 20 bytes being the default setting. The code currently expects only 10 byte frames.

[rajatsrao]

@sdroege , does your commit: a565ecf already fix this issue? It's been a while since I tried this and I'm pretty sure I didn't have your commit at that point (maybe I only tried the master branch)

[sdroege]

Sounds like it, just give it a try maybe? :)