Fixing a comment error and adding a trivial protected destructor.

[SVN r57379]

include/boost/exception/detail/exception_ptr_base.hpp

@@ -19,6 +19,10 @@ boost
 
                         virtual void _rethrow() const=0;
                         virtual bool _empty() const=0;
+
+                        protected:
+
+                        ~exception_ptr_base() throw() { }
                         };
                 }
     }