Add wxTreeCtrl::{Clear,Set}FocusedItem().

Allow changing just the currently focused (not selected) item and also
removing the focus completely.

Closes #11599.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64196 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/treectrl/treetest.h

@@ -212,6 +212,8 @@ public:
     void OnSelectChildren(wxCommandEvent& event);
 #endif // NO_MULTIPLE_SELECTION
     void OnSelectRoot(wxCommandEvent& event);
+    void OnSetFocusedRoot(wxCommandEvent& event);
+    void OnClearFocused(wxCommandEvent& event);
     void OnDelete(wxCommandEvent& event);
     void OnDeleteChildren(wxCommandEvent& event);
     void OnDeleteAll(wxCommandEvent& event);
@@ -355,6 +357,8 @@ enum
     TreeTest_Select,
     TreeTest_Unselect,
     TreeTest_SelectRoot,
+    TreeTest_ClearFocused,
+    TreeTest_SetFocusedRoot,
     TreeTest_SelectChildren,
     TreeTest_ShowFirstVisible,
     TreeTest_ShowLastVisible,