Major codec API update:
Automatically map OpalMediaOptions to SIP/SDP FMTP parameters.
Automatically map OpalMediaOptions to H.245 Generic Capability parameters.
Largely removed need to distinguish between SIP and H.323 codecs.
New mechanism for setting OpalMediaOptions from within a plug in.
Fixed removal of H.323 capabilities just because media format name is a
substring of capability name.
Fixed inadequacies in H.245 Generic Capabilities (must be able to
distinguish between TCS, OLC and ReqMode).