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

[Anthony Walter]

>>     SetWindowLong(Wnd, GWL_USERDATA, Integer(BaseWindow));
>
> Not 64-bits safe. An integer is not a long.  Ptruint probably.

Ah well, there is a new API to fix this in 64 bit Windows. Use
SetWindowLongPtr/GetWindowLongPtr instead.