Provide support for the FTDI serial properties.

Provide support for the FTDI serial properties.

This patch makes it possible to use -mode, -handshake and -xchar in
the fconfigure command similar to using direct serial
lines. Additionally I extended the open procedure to set the defaults
to 19200,n,8,1 no handshake and standard xon/xoff chars. If you know
about another way of doing these things please let me know.

The -xchar option is currently only supporting chars in the range from
1 .. 127 dec, maybe you know of a way how to extend this to at least
the full ASCII charset (I'm obviously no expert in encodings ;-).

Signed-off-by: Leopold Gerlinger <leopold.gerlinger@siemens.com>
Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>