typedef for payload type

[robin-raymond]

Payload type should be an octet by typedef:

typedef octet PayloadType;

So we can define the legal payload values with reference to RFC.

[aboba]

Proposal:

typedef octet payloadtype;

dictionary RTCRtpUnhandled {
unsigned long ssrc;
payloadtype payloadType;
DOMString receiverId;
};

dictionary RTCRtpCodecCapability {
DOMString name = "";
DOMString kind;
unsigned long clockRate;
payloadtype preferredPayloadType;
unsigned long numChannels = 1;
sequence rtcpFeedback;
Dictionary parameters;
Dictionary options;
unsigned short maxTemporalLayers = 0;
unsigned short maxSpatialLayers = 0;
boolean svcMultiStreamSupport = false;
};

dictionary RTCRtpCodecParameters {
DOMString name = "";
payloadtype payloadType;
unsigned long clockRate;
unsigned long numChannels = 1;
sequence rtcpFeedback;
Dictionary parameters;
};