QML dynamic properties depend on Qt private symbols on MSVC

Dynamic properties are implemented using the QMetaObjectBuilder class, which on platforms other than MSVC is built from QtMobility code and has no issues. However, on MSVC we depend on the private symbols of Qt being present, which introduces issues if/when these symbols change.

In Qt mainline at present, after ffd499eb6ff64, the setDynamic method from QMetaPropertyBuilder was removed, which now breaks the build on MSVC. This dependency on Qt private symbols should be removed to avoid future breakages.