nxagent: drop unused nxagentVisibility variables

nx-X11/programs/Xserver/hw/nxagent/Events.c

@@ -2067,8 +2067,6 @@ FIXME: Don't enqueue the KeyRelease event if the key was not already
         if (nxagentOption(Fullscreen))
         {
           nxagentVisibility = VisibilityUnobscured;
-          nxagentVisibilityStop = False;
-          nxagentVisibilityTimeout = GetTimeInMillis() + 2000;
         }
 
         /*

nx-X11/programs/Xserver/hw/nxagent/Window.c

@@ -80,8 +80,6 @@ int nxagentWindowPrivateIndex;
  */
 
 int nxagentVisibility = VisibilityUnobscured;
-unsigned long nxagentVisibilityTimeout = 0;
-Bool nxagentVisibilityStop = False;
 
 ConfiguredWindowStruct *nxagentConfiguredWindowList;
 StaticResizedWindowStruct *nxagentStaticResizedWindowList;

nx-X11/programs/Xserver/hw/nxagent/Windows.h

@@ -256,8 +256,6 @@ void nxagentConfigureWindow(WindowPtr pWin, unsigned int mask);
  */
 
 extern int nxagentVisibility;
-extern unsigned long nxagentVisibilityTimeout;
-extern Bool nxagentVisibilityStop;
 
 /*
  * Return the pointer to the window given the remote id. It tries to