extract (and expand and clean up and document) the header window implementation used inside the generic wxDataViewCtrl in a separate wxHeaderCtrl class which could be reused in (generic) wxListCtrl and, most importantly, wxGrid later

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57093 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/test.bkl

@@ -108,9 +108,10 @@
             geometry/point.cpp
             config/config.cpp
             controls/comboboxtest.cpp
+            controls/headerctrltest.cpp
+            controls/listctrltest.cpp
             controls/textctrltest.cpp
             controls/textentrytest.cpp
-            controls/listctrltest.cpp
             image/rawbmp.cpp
             html/htmlwindow.cpp
             misc/guifuncs.cpp