Fix regression in QML string list concatenations

String lists and other QList property types (wrapped as QQmlSequence) should
behave like arrays and have the Array prototype. Therefore it should be
possible to pass them also as parameter to concat and they get composed
correctly, i.e. the individual items get appended instead of the list being
appened as one item. In the spec for concat this "special" casing should be
applied if the "class internal property" is "Array", and concat appears to be
the only place where this check is done. Therefore this patch adds another
exception to match the expected behavior in QML and extends the "internal
class is Array" meaning to QML list types.

This is a regression from Qt <= 5.1.x

Task-number: QTBUG-33149

Change-Id: Iab9522ac3c4ae6b746e790a99d87501b1cc1b655
Reviewed-by: Michael Brasser <michael.brasser@live.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>