ripper/lexer.rb: dispatch alias

* ext/ripper/lib/ripper/lexer.rb: alias same methods instead of
  eval for each events.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52776 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/ripper/lib/ripper/lexer.rb

@@ -60,12 +60,12 @@ class Ripper
 
     private
 
+    def _push_token(tok)
+      @buf.push [[lineno(), column()], __callee__, tok]
+    end
+
     SCANNER_EVENTS.each do |event|
-      module_eval(<<-End, __FILE__+'/module_eval', __LINE__ + 1)
-        def on_#{event}(tok)
-          @buf.push [[lineno(), column()], :on_#{event}, tok]
-        end
-      End
+      alias_method "on_#{event}", :_push_token
     end
   end