temporary hack added to check for packets that look like RTPv2
packets and to dissect them as such (the right fix is to support
starting and ending frames in conversations and to have H.245
close UDP conversations when appropriate and start new ones);
add preferences for the UDP and TCP port numbers;
add a preference to specify whether to use pre-corrigendum T.38
or post-corrigendum T.38;
give a summary in the Info column.
svn path=/trunk/; revision=9622
Guy Harris