marsond (fix Shift/Enter key for Marson/USBLink PS/2=>USB adaptor).

marsond is a daemon for Linux that fixes an issue with a particular
model of PS/2 => USB keyboard adaptor, the MT606-1 (aka "Marson
Keyboard and Mouse Link", aka USBLink). The symptoms: in games and
emulators, the Enter key only works sometimes, and pressing Shift
and Enter simultaneously makes the Shift key "stick".

marsond uses a udev rule to start automatically when the adaptor is
plugged in. If the vendor and product IDs of your broken adaptor don't
match the ones in /etc/udev/rules.d/99-marsond.rules, you can edit the
IDs in that file and run "udevadm control --reload".

If you're upgrading from an older version of marsond on a machine
where the daemon is still running, the easiest thing to do is unplug
the adaptor and plug it back into the USB port. You could also
(as root) "killall marsond" and then manually start it by running
"marsond".
