Add HTTP Live Streaming playback

This add full support for HTTP Live Streaming playback as per http://tools.ietf.org/html/draft-pantos-http-live-streaming-04.
This includes:
- Automatic fallback to lower bandwidth streams if available, the changeover will be detected according to the network bandwidth
- Full support for live streaming
- Seek support for video on demand stream

There are few problems remaining however:
-When switching to a different stream that is of a different resolution, playback will usually fail. Detection for format change should be added to myth player
-When seeking with values over 2 minutes, sometimes the player will fail, detecting an EOF. No idea why.
-For VOD streams, the whole downloaded content is buffered in RAM, this could get huge (as big as the file being streamed). Caching to disk should be implemented

Playback of AES-128 encrypted content hasn't been tested; retrieval of the key will only work from publicly accessible web site defeating the whole purpose of encryption