* Split I/O feature

   Allow to split input and output so that it is possible to manage these
   independently.

   The general idea is to redirect the output stream on the socket port number
   specified but then redirect the input stream on the same port number + 1.

   Example:

    $ tio /dev/ttyUSB0 --socket inet:4444,split-io

   Will result in output stream being hosted on port 4444 and input stream
   hosted on port 4445.

   For file sockets something similar can be arranged:

    $ tio /dev/ttyUSB0 --socket unix:/tmp/tio-socket-0,split-io

   Will result in output stream being hosted via /tmp/tio-socket-0 and input
   stream hosted via /tmp/tio-socket-0_input

 * Websocket support

   Extend the socket feature to redirect serial I/O to websocket on e.g. port
   1234 like so:

    $ tio --socket ws:1234

   Use libwesockets to implement feature.

 * RS-485 support

   Many modern RS-485 devices such as the ones from FTDI already operate in
   RS-485 mode by default and will work with tio out of the box. However, there
   are still some RS-232/485 devices which need to be switched from e.g. RS-232 to
   RS-485 mode to operate accordingly on the physical level.

   To enable RS-485 mode on such serial devices the idea is to add a --rs-485
   option.