NX_CUT_BUFFER_SERVER is used for communication to nxclient

[uli42]

In Splash.c and Window.c there's code like this:

    /*
     * Send a SetSelectionOwner request
     * to notify of the agent start.
     */

    XSetSelectionOwner(nxagentDisplay, serverCutProperty,
                           nxagentDefaultWindows[i], CurrentTime);

The old nxagent changelog contains this:

nxagent-1.4.0-50

- Now we take the ownership of the selection
  on "NX_CUT_BUFFER_SERVER" twice, in order
  to solve bug in communication with nxclient
  to let him see our main window and know that
  agent established connection with X server.

NXdispatch.c contains this:

    /*
     * Set NX_WM property (used by NX client to identify
     * the agent's window) three seconds since the first
     * client connects.
     */

    nxagentWMtimeout = GetTimeInMillis() + 3000;
...
        if (!nxagentWMPassed && (nxagentWMtimeout < currentDispatch))
        {
           nxagentRemoveSplashWindow();
        }

nxagentRemoveSplashWindow() will run XSetSelectionOwner(...serverCutProperty...).

As we are not using nomachine's nxclient and x2goclient uses a different approach we could probably drop this "miususe" of an clipboard related property.