Made progress on PR-8210 code

Last night, I've wrote a lot of the Dexter code for PR-8210 support.  It should be able to now correctly interpret incoming pulses on the wire and convert those into messages.  I still need to take the interpreter inside Daphne and modify it so it can be used with Dexter but that shouldn't be too hard.  Unfortunately, I don't have any arcade hardware which used the PR-8210 so I have nothing to test it with.  I plan on rigging up my STK600 to add as a controller.  I will need to find a jack that plugs into the PR-8210 port on the Dexter board and modify it so it can be plugged into the PR-8210.  I've gotta have a cable lying around here somewhere that will fit.  Interpreting the PR-8210 is actually pretty trivial compared to something like the VP-931 but not having an authentic way to test it is a pain.  Fortunately, Warren can test it on his Cobra Command Cliff Hanger conversion board set and at least verify that it works for one PR-8210 game.