Change from 28/11/2014.

Changelog:
2014.11.28:
- When "RTSPClient" parses a RTSP response, we first skip over any blank lines that may be at
  the start of the response.  This can happen if the previous response (e.g., to a "DESCRIBE")
  contained extra whitespace.
  (Thanks to ilwoo Nam for giving an example of a server that exhibited this behavior.)