Fix the tl_start() routine; sometimes the tl_tx_tail pointer was not being updated correctly.
Fix the tl_start() routine; sometimes the tl_tx_tail pointer was not
being updated correctly.

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