add modelines to .hxx files as well

sdext/source/presenter/PresenterNotesView.hxx

@@ -1,3 +1,4 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
 /*************************************************************************
  *
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
@@ -195,3 +196,5 @@ private:
 } } // end of namespace ::sdext::presenter
 
 #endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */