Use getter functions to get access to some properties of wxPropertyGridPageState.

Use existing GetColumnCount(), GetColumnWidth() functions instead of getting direct access to corresponding member variables.

include/wx/propgrid/propgrid.h

@@ -994,7 +994,7 @@ public:
     */
     unsigned int GetColumnCount() const
     {
-        return (unsigned int) m_pState->m_colWidths.size();
+        return m_pState->GetColumnCount();
     }
 
     /** Returns colour of empty space below properties. */