Filters out repeating '_' messages from the host port.
Implements response sending for getfn and setfn/speed commands that fall outside of the capabilities of the mobile station.
Makes fn 0x20 and 0x21 be "known" to the mobile station. They will map to nonexistant DCC functions 29 and 30, which will trigger a deterministic '0' response.
Enables automata running code.
Adds proper control flow priorities to the main executor.