Add Method#original_name code example [ci skip]

* proc.c (method_original_name): [DOC] add code example.
  [Fix GH-1693]

Author:    Seiei Miyagi <hanachin@gmail.com>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59720 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

proc.c

@@ -1606,6 +1606,12 @@ method_name(VALUE obj)
  *     meth.original_name    -> symbol
  *
  *  Returns the original name of the method.
+ *
+ *    class C
+ *      def foo; end
+ *      alias bar foo
+ *    end
+ *    C.method(:bar).original_name # => :foo
  */
 
 static VALUE