3009: Registration of parityfec MIME types.

The RTP (Real-time Transport Protocol) payload format for generic forward error correction allows RTP participants to improve loss resiliency through the use of traditional parity-based channel codes. This payload format requires four new MIME types, audio/parityfec, video/parityfec, text/parityfec and application/parityfec. This document serves as the MIME type registration for those formats.