dix: Call RealizeCursor during InitializeSprite.

RealizeCursor should be called when the cursor is allocated. However, when the
root cursor is allocated, no devices exist yet, and thus RealizeCursor is
never called. This may lead to segfaults lateron in DDXes like Xnest that
actually need to do something for each cursor, and lateron rely on that
DDX-specific data for each cursor has been initialized.

dix/events.c

@@ -2950,6 +2950,7 @@ InitializeSprite(DeviceIntPtr pDev, WindowPtr pWin)
 
     if (pScreen)
     {
+        (*pScreen->RealizeCursor) ( pDev, pScreen, pSprite->current);
         (*pScreen->CursorLimits) ( pDev, pScreen, pSprite->current,
                                    &pSprite->hotLimits, &pSprite->physLimits);
         pSprite->confined = FALSE;