Rename rs232_in_qeue_clear to rs232_flush_qeue

Signed-off-by: Petr Štetiar <ynezz@true.cz>
Windows: Set the timeout values only if not already set

Previous approach was quite wrong as we've been setting the timeout values
always before each read/write operation. Now we check if the values did
changed and make the changes afterwards.

I've renamed the functions to better descriptive ones:

	port_timeout -> port_set_timeouts
	port_buffers -> port_set_buffers

Signed-off-by: Petr Štetiar <ynezz@true.cz>
Fix build of timer code on vs2005

Signed-off-by: Petr Štetiar <ynezz@true.cz>