Fix bug #314:

- remove most of the metaprogramming kung fu in MathFunctions.h (only keep functions that differs from the std)
- remove the overloads for array expression that were in the std namespace

unsupported/Eigen/AlignedVector3

@@ -167,7 +167,8 @@ template<typename _Scalar> class AlignedVector3
 
     inline Scalar norm() const
     {
-      return internal::sqrt(squaredNorm());
+      using std::sqrt;
+      return sqrt(squaredNorm());
     }
 
     inline AlignedVector3 cross(const AlignedVector3& other) const