[Lazarus] WinControl.CanFocus

[Juha Manninen]

Regarding issue:
  http://bugs.freepascal.org/view.php?id=21708

I would like to fix the bug as proposed by Zoran Vučenović and Ondrej Pokorny.
Opinions?

The current behavior is compatible with Delphi. However it conflicts
with even Embarcadero's own documentation which means it clearly is a
bug in Delphi.
We should not replicate Delphi's bugs IMO.

The changed behavior would affect existing code, at least in theory.
In practice the CanFocus method is useless, no code can use it for its
intended purpose. Thus the implication would be very small.

Juha