It isn't possible to send media if a MediaEngine has no codecs. This
catches a common misconfiguration issues that users find themselves in.
Resolves#1702
ReadDeadline is supported by RTPReceiver but not RTPSender. This
commit attempts to provide similar method for RTPSender.
If SetReadDeadine is called with:
- an empty time.Time: it will clear all previous set deadline.
- a non-empty time.Time: it will abort all pending "ReadRTCP" calls if
the specified time is up.
Previously, Reading RTP or RTCP packets from a peer
would block until a packet was received, or the
connection was terminated. This change allows you to
set a deadline, after which the read function will
return a timeout error and you can get on with other
things.
Resolves#1553
