add null class for template specialization

src/Core/ClassComposite.h

@@ -122,7 +122,7 @@ struct ClassComposite {
 } // detail
 
 
-struct Null {};
+//struct Null {};
 template < typename T0 = Null,
            typename T1 = Null,
            typename T2 = Null,

src/Core/ClassCompound.h

@@ -4,6 +4,7 @@
 
 #include "boost/type_traits.hpp"
 
+#include "Core/Types.h"
 #include "Core/Mpl.h"
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -83,7 +84,7 @@ struct ClassCompound : ULIB_MPL_INHERIT_SEQ(_Seq) {
 ////////////////////////////////////////////////////////////////////////////////
 // COMPOUND SPECIALIZATIONS //
 
-struct Null {};
+//struct Null {};
 template < class T0 = Null,
            class T1 = Null,
            class T2 = Null,

src/Core/Types.h

@@ -322,7 +322,8 @@ struct PrintTypeId {
 struct                    Access  {};
 template <class T> struct Access2 {};
 
-
+// NULL CLASS //
+struct Null {};
 
 
 } // uLib