Don't provide typehint in QQmlExpression::evaluate()

Don't provide typehint in QQmlExpression::evaluate()

Previously, the result returned by QQmlExpression::evaluate() was
converted from the actual JavaScript result with a default typehint
of QList<QObject*>.  This commit removes that typehint so that the
engine's conversion code will choose the most appropriate return type
for the result JavaScript value, instead.

Task-number: QTBUG-17082
Change-Id: I368a018b235e9e001b1b92db3699de377748b74f
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>