More options for TXINH #enhancement

[frank-g-o]

Full duplex dual band radios like TM-D710 have to block Direwolf from sending when the "other" band of the radio is transmitting. For example when using both the internal TNC and external Direwolf TNC. For this, the SQL output of the D710 can signal a busy state when the radio is transmitting on the other band. Most external audio interfaces provide this SQL info as DCD or CTS signal on the (virtual) serial port. When TXINH supports DCD or CTS as extra input options, next to the GPIO pin, no additional hardware is needed when using such an external audio interface. Can this be implemented in a next release? Best 73 de Frank DH4FR/PA4FR