Changes

rtp_extensions.h: update for TW-TS-003 version 1.1.0

Themyscira Wireless released new specs for enhanced RTP formats
on AoIP interface user plane:

* TW-TS-006 for AMR, allowing RTP transport between an E1 BTS and
  a CN transcoder that implements both regular transcoding and TFO
  functions as specified in 3GPP Rel4 for TDM-based GSM;

* TW-TS-007 for compressed CSD, making CSD in RTP much more efficient;

* An updated version of TW-TS-003 adds two new bits to RTPext IE
  (GSM0808_IE_THEMWI_RTP_EXTENSIONS) for MSC to request the use of
  TW-TS-006 and TW-TS-007 extensions, and for BSS to acknowledge
  the necessary support.

All TW-TS for RTP extensions are summarized here:

https://osmocom.org/projects/retro-gsm/wiki/ThemWi_RTP_Extensions

Change-Id: I2cc2c9340f9fa5c7111447a6beef49c335fa1107