fecrizzo: new FEC elements ported from Farsight

Submitted by Aleix Conchillo Flaqué

Link to original bug (#730268)

Description

This plugin was initially written for Farsight for GStreamer 0.10 by Olivier Crete. It has been ported to GStreamer 1.0 along with bug fixes and memory issues.

It provides an encoder and decoder that can be dynamically added as RTP
AUX senders and receivers using the new rtpbin API.