Update xl(4) man page to mention a whole bunch of supported cards, including the 3c556 and 3c556B.
Update xl(4) man page to mention a whole bunch of supported cards,
including the 3c556 and 3c556B.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase