[Lazarus] Lazarus forces HALFTONE StretchBldMode in StretchMaskBlt/for alpha-enabled DC (and doesn't for non-alpha)

[Flávio Etrusco]

Hello,
while looking into bug http://bugs.freepascal.org/view.php?id=20226 I
realized that Lazarus has the following call in
TWin32WidgetSet.StretchMaskBlt:
  Windows.SetStretchBltMode(DestDC, STRETCH_HALFTONE);

I wonder whether it should be forced at all, but if it does, I think
it should have the same value for both alpha/masked and non-masked?
Also, I would think this change was meant for better default behavior
of drawing bitmaps to controls. Could it just be initialized in e.g.
TControlCanvas.CreateHandle?

Best regards,
Flávio