Reevaluate TivaDCC Driver RailCom Cutout Workarounds for Backward Compatibility

[bakerstu]

The original TivaDCC driver provides an option to insert a DCC half zero bit pattern after the RailCom cutout. This is known to help some older decoders resynchronize to the preamble following a RailCom cutout. It has also been determined that the half zero bit pattern does not work well with some other older decoder.

The workaround was change to be a DCC full zero. This has been tested to work successfully with decoders that originally required the half zero as well as now working with decoders that have trouble with the half zero. It seems to be a true superset for compatibility.

However, there isn't much field data to validate this fix. Therefore it should be reevaluated in the future to see if the fix has unintended consequences or needs altered in some way for wider compatibility.