[Qt5-feedback] QAnchorLayout

[Philippe]

In the same way there is a "QGraphicsAnchorLayout", I wish there could
be also a "QAnchorLayout" for widgets.

After 4.6 was released, I was told this would happen in a future release,
but I have seen no mention of it later. 

I have understood that widget stuff is not a priority anymore, but I
believe that class would be important to add. That's maybe the only thing I am
missing in the classical widget classes.

Philippe