There might be cycles in the prototype chain.
In this case the meta info is invalid.

setupPrototypes() now flags the meta info as
invalid in this case.

If not we risk a stack overflow when running the
parent chain (Which might have a cycle then.)

Task-number: QTCREATORBUG-8399
Change-Id: Ie9f6bfc39cdfd1365463a70e76081d53df33da7f
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>