[functionals.l2] modernize static checks

dune/gdt/functionals/l2.hh

@@ -36,16 +36,9 @@ namespace internal {
 template <class FunctionType, class VectorImp, class SpaceImp, class GridViewImp, class LocalEvaluationType>
 class L2VolumeTraits
 {
-  static_assert(std::is_base_of<Stuff::LocalizableFunctionInterface<
-                                    typename FunctionType::EntityType, typename FunctionType::DomainFieldType,
-                                    FunctionType::dimDomain, typename FunctionType::RangeFieldType,
-                                    FunctionType::dimRange, FunctionType::dimRangeCols>,
-                                FunctionType>::value,
+  static_assert(Stuff::is_localizable_function<FunctionType>::value,
                 "FunctionType has to be derived from Stuff::LocalizableFunctionInterface!");
-  static_assert(std::is_base_of<SpaceInterface<typename SpaceImp::Traits, SpaceImp::dimDomain, SpaceImp::dimRange,
-                                               SpaceImp::dimRangeCols>,
-                                SpaceImp>::value,
-                "SpaceImp has to be derived from SpaceInterface!");
+  static_assert(is_space<SpaceImp>::value, "SpaceImp has to be derived from SpaceInterface!");
 
 public:
   typedef L2Volume<FunctionType, VectorImp, SpaceImp, GridViewImp, LocalEvaluationType> derived_type;