Correct compilation errors on recent ITK

Common/itkNumericTraitsTensorPixel2.cxx

@@ -58,6 +58,8 @@ namespace itk
 
   Tensor< double,3 > NumericTraits<Tensor<double, 3> >::ZeroValue() { return Zero; }
 
+  Tensor< long double,3 > NumericTraits<Tensor<long double, 3> >::ZeroValue() { return Zero; }
+
   Tensor< double,3 > NumericTraits<Tensor<double, 3> >::min() { return vcl_numeric_limits<double>::min(); }
 
   Tensor< double,3 > NumericTraits<Tensor<double, 3> >::max() { return vcl_numeric_limits<double>::max(); }

Common/itkNumericTraitsTensorPixel2.h

@@ -411,6 +411,7 @@ public:
   typedef Tensor<long double, 3> RealType;
   typedef long double ScalarRealType;
   static const Tensor< long double,3 > ITK_EXPORT Zero;
+  static Tensor< long double,3 > ZeroValue();
   const static bool is_integer=false;
 };