This is just a minor change to wxDockIt to allow for hiding the close button in the panel when a wxDockWindow is docked (residing in a wxDockPanel).
After applying the patch, make sure to include dockpanel.h in your project along with all your usual wxDockIt headers, and pass in wxDPC_NO_CLOSE window style.
The patch can be found in the wxExtended SF project page here:
[ 1222222 ] Option to hide the close button when docked.