Bug #1788: Fix rule-of-three violations inside the stable modules.

This fixes deprecated-copy warnings when compiling with GCC>=9
Also protect some additional Base-constructors from getting called by user code code (#1587)

Eigen/src/Core/Transpose.h

@@ -153,6 +153,8 @@ template<typename MatrixType> class TransposeImpl<MatrixType,Dense>
     {
       return derived().nestedExpression().coeffRef(index);
     }
+  protected:
+    EIGEN_DEFAULT_EMPTY_CONSTRUCTOR_AND_DESTRUCTOR(TransposeImpl)
 };
 
 /** \returns an expression of the transpose of *this.