...otherwise, GCC 6 would aggressively inline ScValidationDlg destruction of the
VclPtr<ScValidationDlg> in ScValidityRefChildWin::ScValidityRefChildWin
(sc/source/ui/view/reffact.cxx, in sc library), checking whether the vtable
points at ~ScValidationDlg (instead of a derived class dtor) to directly inline
the ~ScValidationDlg code, which requires the ScValidateionDlg vtable (to store
it in the object's vtable during destruction), which requires the code of inline
virtual ScValidationDlg::dispose and ScValidationDlg::Close, which in turn need
the addresses of (non-inline) ScValidationDlg::RemoveRefDlg and
ScTPValidationValue::RemoveRefDlg, both defined in the scui library and not
exported from there.

Change-Id: I7eb96f42deb5edd844d91e999aa5511679302c01