Add wxDataViewListCtrl::GetItemCount().

This method is convenient and (almost, except for the return value) compatible
with wxListCtrl.

See #11088.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71563 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dataview.h

@@ -972,6 +972,8 @@ public:
     void DeleteItem( unsigned int pos );
     void DeleteAllItems();
 
+    unsigned int GetItemCount() const;
+
     void SetItemData( const wxDataViewItem& item, wxUIntPtr data );
     wxUIntPtr GetItemData( const wxDataViewItem& item ) const;
 
@@ -1085,6 +1087,9 @@ public:
     wxUIntPtr GetItemData( const wxDataViewItem& item ) const
         { return GetStore()->GetItemData( item ); }
 
+    int GetItemCount() const
+        { return GetStore()->GetItemCount(); }
+
     void OnSize( wxSizeEvent &event );
 
 private: