serial: fix blocking call on ports, esp. on win32

Summary from Lada:

On Win7, good testing command is:
C:\hamlib> rigctl -vvvvv -m 214 -r COM1 -s 4800 -C data_bits=8 -C
stop_bits=2 -C serial_handshake=Hardware -C timeout=1000

Behavior of this command differs on COM port. On hardware ports
(onboard, PCI NetMos, all probably 16550-compatible) rigctl freeze in
data write. It is correct, no hardware handshake is estabilished. On
FT232 USB port initialization failed by timeout. I think it is not
correct but this is not subject of this e-mail.

Looked into hamlib source and found, that timeout argument is no
longer handled. SetCommTimeouts takes timeout from c_cc[VTIME] which
is not filled.

Signed-off-by: Ladislav Vaiz <spam@nagano.cz>