RRScreenChangeNotify events required

[uli42]

When starting a rootless NX session inside a VMware (now Omnissa) Horizon VDI session the rootless session will not get informed when the Horizon window resized. This is because nxagent is not registering for RRScreenChangeNotify events - despite having (disabled) code in Events. that can handle those events.

Adding this support should be straight forward but testing this for side effects on other setups might be tricky...