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

Eigen/src/SparseCholesky/SimplicialCholesky.h

@@ -746,6 +746,8 @@ template<typename Derived>
 template<bool DoLDLT>
 void SimplicialCholeskyBase<Derived>::factorize_preordered(const CholMatrixType& ap)
 {
+  using std::sqrt;
+  
   eigen_assert(m_analysisIsOk && "You must first call analyzePattern()");
   eigen_assert(ap.rows()==ap.cols());
   const Index size = ap.rows();
@@ -830,7 +832,7 @@ void SimplicialCholeskyBase<Derived>::factorize_preordered(const CholMatrixType&
         ok = false;              /* failure, matrix is not positive definite */
         break;
       }
-      Lx[p] = internal::sqrt(d) ;
+      Lx[p] = sqrt(d) ;
     }
   }