don't pretend that break()/next()/return() are functions

it's a pretty braindead thing to implement control flow statements as
(built-in) functions.

as a "side effect", this fixes return() value handling for lists.

(cherry picked from qtcreator/f53ed6c4b3feca59a94d4f0de8b1a7411122e30e)
(cherry picked from qtcreator/f529e22ec38fb9a656d74394e484d2453cf42c69)
Change-Id: I59c8efa0e4d65329327115f7f8ed20719e7f7546
Reviewed-by: Qt Doc Bot <qt_docbot@qt-project.org>
Reviewed-by: Joerg Bornemann <joerg.bornemann@nokia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
(cherry picked from qtbase/8400896cfe3fbef7666329a2920bd0dbdd5890af)
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>