Column numbers of signals in Connection objects are wrong

The column numbers seem to be always reported as 2 by the QV4::Function objects in those instances of QQmlBoundSignalExpression. This is exposed by 2520879f0b58779027589d491eb47e98e0872b5a, which prefers the QV4::Function over the internally kept column number if available. The column numbers kept in the QQmlBoundSignalExpression are correct.