Get rid of include directives inside namespace blocks (bug #339).

Eigen/src/Eigen2Support/Block.h

@@ -26,6 +26,8 @@
 #ifndef EIGEN_BLOCK2_H
 #define EIGEN_BLOCK2_H
 
+namespace Eigen { 
+
 /** \returns a dynamic-size expression of a corner of *this.
   *
   * \param type the type of corner. Can be \a Eigen::TopLeft, \a Eigen::TopRight,
@@ -134,4 +136,6 @@ DenseBase<Derived>::corner(CornerType type) const
   }
 }
 
+} // end namespace Eigen
+
 #endif // EIGEN_BLOCK2_H