merge 'threv' and 'rev' variables in print-tcp into just 'rev'
OpenFlow 1.0: add OFPT_VENDOR messages test case

This capture was produced using an Arista DCS-7050Q-16 switch running
EOS-4.10.4 software. The controller sends two vendor messages
(BSN_GET_IP_MASK_REQUEST and BSN_GET_MIRRORING_REQUEST) and the switch
sends a reply for each (BSN_GET_IP_MASK_REPLY and
BSN_GET_MIRRORING_REPLY respectively).