Adjust XDamage tracking to geometry

We might have an offset in the area of the screen we're tracking,
so make sure that offset is included in the changes we report.
diff --git a/unix/x0vncserver/XDesktop.cxx b/unix/x0vncserver/XDesktop.cxx
index 5f67f29..fa5adf4 100644
--- a/unix/x0vncserver/XDesktop.cxx
+++ b/unix/x0vncserver/XDesktop.cxx
@@ -611,6 +611,8 @@
 
     dev = (XDamageNotifyEvent*)ev;
     rect.setXYWH(dev->area.x, dev->area.y, dev->area.width, dev->area.height);
+    rect = rect.translate(Point(-geometry->offsetLeft(),
+                                -geometry->offsetTop()));
     server->add_changed(rect);
 
     return true;