Add wxDataViewCtrl::{Set,Get}CurrentItem().

Current item is the same as the selected item in single selection mode but in
multiple selection mode there was no way to neither get this item nor change
it before so add the new functions to allow doing this now.

The new methods are implemented for the generic, GTK and OS X/Cocoa versions
but only stubs are provided for OS X/Carbon.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65228 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/carbon/dataview.h

@@ -403,6 +403,8 @@ public:
  //
  // selection related methods (inherited from wxDataViewWidgetImpl)
  //
+  virtual wxDataViewItem GetCurrentItem() const;
+  virtual void SetCurrentItem(const wxDataViewItem& item);
   virtual int  GetSelections(wxDataViewItemArray& sel)   const;
   virtual bool IsSelected   (wxDataViewItem const& item) const;
   virtual void Select       (wxDataViewItem const& item);

include/wx/osx/cocoa/dataview.h

@@ -471,6 +471,8 @@ public:
     //
     // selection related methods (inherited from wxDataViewWidgetImpl)
     //
+    virtual wxDataViewItem GetCurrentItem() const;
+    virtual void SetCurrentItem(const wxDataViewItem& item);
     virtual int  GetSelections(wxDataViewItemArray& sel)   const;
     virtual bool IsSelected(const wxDataViewItem& item) const;
     virtual void Select(const wxDataViewItem& item);

include/wx/osx/core/dataview.h

@@ -85,6 +85,9 @@ public:
  //
  // selection related methods
  //
+  virtual wxDataViewItem GetCurrentItem() const = 0;
+  virtual void SetCurrentItem(const wxDataViewItem& item) = 0;
+
   virtual int  GetSelections(wxDataViewItemArray& sel)   const = 0; // returns all selected items in the native control
   virtual bool IsSelected   (wxDataViewItem const& item) const = 0; // checks if the passed item is selected in the native control
   virtual void Select       (wxDataViewItem const& item)       = 0; // selects the passed item in the native control

include/wx/osx/dataview.h

@@ -174,7 +174,6 @@ public:
   virtual void Expand(const wxDataViewItem& item);
   virtual bool IsExpanded(const wxDataViewItem & item) const;
 
-
   virtual unsigned int GetCount() const;
   virtual wxRect GetItemRect(const wxDataViewItem& item, const wxDataViewColumn* columnPtr) const;
   virtual wxDataViewItem GetSelection() const;
@@ -279,6 +278,9 @@ private:
  // initializing of local variables:
   void Init();
 
+  virtual wxDataViewItem DoGetCurrentItem() const;
+  virtual void DoSetCurrentItem(const wxDataViewItem& item);
+
  //
  // variables
  //