doc and use sed to clean the class hierarchy instead of

preprocessor directives.

Eigen/src/Core/Part.h

@@ -59,11 +59,7 @@ struct ei_traits<Part<MatrixType, Mode> >
 };
 
 template<typename MatrixType, unsigned int Mode> class Part
-#ifndef EIGEN_PARSED_BY_DOXYGEN
   : public MatrixBase<Part<MatrixType, Mode> >
-#else
-  : public MatrixBase
-#endif
 {
   public: