Put port param back in OS_serial_<func>

Only support one port at the moment, but put the param back for later
(maybe).
Added URL for more info
Serial changes

Move serial handling into main event loop.
Support CLOSE SERIAL
Remove file "records" - byte streams are better!

Note. We cannot hang onto any references to the flash between read
calls because it may get compacted, invalidating these references.
Hex