implement wxTreeCtrl::ItemHasChildren() properly for virtual root item; added unit test for it

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58177 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/test_test_gui.dsp

@@ -319,6 +319,10 @@ SOURCE=.\controls\textctrltest.cpp
 
 SOURCE=.\controls\textentrytest.cpp
 # End Source File
+# Begin Source File
+
+SOURCE=.\controls\treectrltest.cpp
+# End Source File
 # End Group
 # End Target
 # End Project