Two bugfixes:

1. the RED packet handling was incorrectly offsetting into final buffer by the total header length instead of the rtp header length.  in theory this matters a lot; in practice, it worked because the size of the red header doesn't seem to be different from the size of the RTP header (???)
2. Not accounting for RTP packet padding in the recorder; RTP packets can (again, in theory) be padded with stuff after the payload.  Strip that off before we hand it down to the rest of the RTP code so it doesn't have to deal with it.
Fix so we don't record corrupted frames.

When there's packet loss, there's a possibility that we end up constructing a corrupted frame and hand that to libav.  The resulting corruption is much worse than if we had just skipped the frame entirely.  This change also fixes audio handling (it was incorrectly computing header size) and optimizes it slightly so we're not doing an unnecessary memcpy.

One side affect of this is we have to examine the VP8 header before we copy it into our unpackage buffer.  This also ends up optimizing stuff slightly though.

Also, zap input processor member variable and audio buffer; we don't need either of these anymore.
Merge pull request #160 from jnoring/master

Two bugfixes: