Add a way to assign something to a pointer

In QtWebEngine, there is the QWebEnginePageauthenticationRequired() signal which has a speciality which can't be used from PySide: In order to abort the authentication, *authenticator (passed in by Qt) [needs to be set|https://github.com/qt/qtwebengine/blob/0f2de1b59bdaae4b9acda10a47698877c8345dc1/src/core/api/qwebenginepage.cpp#L496-L500
] to a null QAuthenticator().

I don't see a way to reassign the pointer without shiboken help, as in Python land, we get authenticator as an object, not a pointer. PyQt has sip.assign(authenticator, QAuthenticator() to do this.

void QWebEnginePage::authenticationRequired(
    const QUrl &requestUrl,  QAuthenticator *authenticator)