Sticky Fn key

[romanprocopie]

This may be a duplicate of issue #50.

Steps to reproduce

1. Connect to a Mac that runs VineVNC of any version (proved with a latest master custom build and a stock version of a couple of years ago), using most probably any VNC client (tested with RealVNC and Guacamole WEB client). It doesn't matter which OS you are connecting from, what is important is use a PC style keyboard on the device you are connecting from.
2. Press q, e, d in a window, like a text editor. Everything works as intended
3. Press Home, End, PgUp or PgDn key on the computer you have connected from.
4. After that keys like d, e, q, etc will produce actions like they were pressed with Fn down (emoji, new note, etc)

I have added a log in VncServer::handleKeyboard and I can see that in terms of key code nothing changes, i.e. the server receives exactly the same keycodes before and after pressing the Home key.

Fn key is not logged at all.

I have also compared that with the WebSocket dump in Google Chrome and that shows the same results.

With a bit of help I might try to fix it, just no more ideas after I added that log.