[Lazarus] Why TDateTimePicker.Checked works as Enabled?

[Ondrej Pokorny]

Feel free to provide patches. Don't forget to check different WidgetSets 
(Win32, Qt, Gtk2, Carbon at least). I'll review them.

Some "strange" behavior may be caused by the fact that some features are 
not supported on all WS and therefore it's better to keep the same 
"strange" behavior everywhere then to have different behavior across WS. 
This may be the case of a checkbox in TDateTimePicker. Also check the 
bug tracker, maybe the bugs have already been reported.

If the same "correct" behavior cannot be achieved in all WS, there is 
still a valid workaround - place an extra checkbox in front of the 
TDateTimePicker. (AFAIR I did the same in Delphi long time ago because I 
had problems with the checked property as well. I don't remember any 
details, though.)

Ondrej