Document how changes of the sizeHint of an ActiveX control are passed on to the container

QAxServer based controls might change their sizeHint after property setters have been called, and then ActiveQt will report the new size requirement to the container (i.e. the webpage), which will typically change the size of the control as requested.

In the case of webpages this is usually not wanted, as the webmaster wants to have control over this. So this should be documented, together with the workaround of reimplementing sizeHint() to return a constant, large enough value.