set the index for BEGIN_DRAG events (patch 726308)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@20418 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/listctrl.cpp

@@ -3148,6 +3148,7 @@ void wxListMainWindow::OnMouse( wxMouseEvent &event )
 
         wxListEvent le( command, GetParent()->GetId() );
         le.SetEventObject( GetParent() );
+        le.m_itemIndex = current;
         le.m_pointDrag = m_dragStart;
         GetParent()->GetEventHandler()->ProcessEvent( le );