Fix valgrind errors in tst_qqmlecmascript::revision

The QML code looks like this:

    MyRevisionedClass {
        prop1: prop2
    }

and MyRevisionedClass is C++ based. We need to return an initialized value when
reading prop2.

Change-Id: I33792c04aa1ba0d8e38c1351b8fb4de7abbe4891
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Don't assert on (++1), rather throw a ReferenceError

Also fix up the generated string for the reference error.

Change-Id: I327a8eb682017297a799f8bae650267727039616
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Fix a bug in the inserting setters

Make sure we have allocated enough storage for
properties before writing them.

Change-Id: I3232ad1c4f17c21b48e8b444dc9ca604745dc799
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>