Switch socket buffering to FIFO to reduce memory usage

[catalinii]

• Switches the socket buffering to use FIFO to simplify the code and reduce memory usage.
• Priority data functionality is preserved (RTSP responses send to the client has priority over regular stream data):
• • There is a special buffer holding priority data
• • When present, the current packet until the next RTSP header is flushed then the priority data, then the flushing of the TS stream continues
• Fixes the tests to include the rtsp header