[fpc-pascal] How to use a window message queue in a call?

[Marco van de Voort]

In our previous episode, Anthony Walter said:
>     BaseWindow := CreationWindow;
>     BaseWindow.FHandle := Wnd;
>     SetWindowLong(Wnd, GWL_USERDATA, Integer(BaseWindow));

Not 64-bits safe. An integer is not a long.  Ptruint probably.