In the heuristic T.124 dissector, catch BoundsError and

In the heuristic T.124 dissector, catch BoundsError and
ReportedBoundsError exceptions when attempting to dissect the first bit
of the packet and, if either is thrown, assume the packet isn't a packet
for what we were trying to dissect, rather than just completely failing.

Return TRUE if the heuristic T.124 dissector recognizes the packet.

Get rid of some _U_s attached to parameters that are, in fact, used.

svn path=/trunk/; revision=46064