Improve wxDataView on DPI change

Fix the row heights after a DPI change and adjust the column widths.
Use DPIChangedEvent instead of MSWUpdateFontOnDPIChange because the child
controls (m_clientArea, m_headerArea) need to update their font sizes first.

include/wx/generic/dataview.h

@@ -316,6 +316,8 @@ protected:
 
     virtual void DoEnableSystemTheme(bool enable, wxWindow* window) wxOVERRIDE;
 
+    void OnDPIChanged(wxDPIChangedEvent& event);
+
 public:     // utility functions not part of the API
 
     // returns the "best" width for the idx-th column