Serial port flow control setting support
GNAT.Serial_Communication.Set now allows the specification of no flow control, hardware (RTS/CTS) flow control, or software (Xon/Xoff) flow control. The default is no flow control. Note that for Linux, the previous behaviour was to always enable RTS/CTS flow control. This must now be specified explicitly if desired. On Linux, the CLOCAL flag (ignore all modem control signals) can also be specified.