Add wxDataViewCtrl::SetRowHeight() and provide its generic implementation.

Allow changing the (fixed) row height without using wxDV_VARIABLE_LINE_HEIGHT
which may slow down the control display too much.

The new method is not implemented for the native GTK and OS X implementations
yet but should be simple to implement there.

See #12749.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67885 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dataview.h

@@ -700,7 +700,9 @@ public:
                                 const wxDataViewColumn *column = NULL ) = 0;
     virtual void HitTest( const wxPoint & point, wxDataViewItem &item, wxDataViewColumn* &column ) const = 0;
     virtual wxRect GetItemRect( const wxDataViewItem & item, const wxDataViewColumn *column = NULL ) const = 0;
-    
+
+    virtual bool SetRowHeight( int WXUNUSED(rowHeight) ) { return false; }
+
     virtual void StartEditor( const wxDataViewItem & WXUNUSED(item),
                               unsigned int WXUNUSED(column) )
         { }