Merge branch 'qt-region-fixes'

wxQt region-related fixes: fix bugs in clipping region handling and
add wxRegion::DoCombine().

See https://github.com/wxWidgets/wxWidgets/pull/1162

include/wx/qt/dc.h

@@ -116,7 +116,7 @@ protected:
     QPainter *m_qtPainter;
     QPixmap *m_qtPixmap;
 
-    wxRegion *m_clippingRegion;
+    wxRegion m_clippingRegion;
 private:
     enum wxQtRasterColourOp
     {

include/wx/qt/region.h

@@ -48,6 +48,8 @@ protected:
     virtual bool DoSubtract(const wxRegion& region);
     virtual bool DoXor(const wxRegion& region);
 
+    virtual bool DoCombine(const wxRegion& rgn, wxRegionOp op);
+
 private:
     wxDECLARE_DYNAMIC_CLASS(wxRegion);
 };