Detect and warn when using QQuickWidget as a native child
Detect and warn when using QQuickWidget as a native child

This is not supported.

Change-Id: I19ed485ee629baa4f3631770ab0c730e0ef6748e
Reviewed-by: Paul Olav Tvete <97541fb6312d77f06e19078c7c70b2c1f75fb828@digia.com>

mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d