Setting the focus doesn't set firstResponder correspondingly

When Qt sets the focus to a widget, the corresponding NSView is not made firstResponder. In the "normal" QWidget application this is no problem, since there is only a single QNSView for each window. It might lead to effects when some widget is forced to be native, but I haven't checked that in detail (it might not be a problem because everything is handled in the Qt-controlled QNSView class). It especially is an issue when embedding a native NSView with QMacCocoaViewContainer.

When clicking on a QWidget, AppKit automatically changes firstResponder due to the mouse event, but when programmatically setting the focus (e.g. from a menu action), the firstResponder stays at the previous NSView, so that receives and handles key events instead of the focus-QWidget.

I've attached a little test application. Give the top NSTextField focus, press cmd+L to set the Qt focus to the QTextEdit, type something. Expected: NSTextField loses focus, QTextEdit receives the keys. Actual: NSTextField keeps focus and receives the keys, QTextEdit doesn't receive the keys even though it thinks that it has keyboard focus.

You can uncomment the two lines in Widget::setFocusToTextEdit() to set the firstResponder correctly, and fix the example.