Issue 189: No IceGatherer.stop()

There is no way to stop an IceGatherer once constructed. Let us say that an Offerer offers both Audio and Video, on distinct ports, and constructs and IceGatherer and IceTransport for them. Then the Answer comes back indicating that the Answerer doesn't want video (port = 0). Wouldn't you want to call .stop() on the IceGatherer and IceTransport? Otherwise you'll have the IceGatherer expending energy gathering Server Reflexive and relay candidates that you'll never use.

Potential fix:

partial interface RTCIceGatherer : RTCStatsProvider {
void stop ();
};

stop
Stops and closes the current object.

No parameters.
Return type: void