fix for POST method.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@2502 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/cgi.rb

@@ -1905,8 +1905,8 @@ The hash keys are case sensitive. Ask the samples.
         else
           at_exit() do
             if defined?(CGI_PARAMS)
-              remove_const(:CGI_PARAMS)
-              remove_const(:CGI_COOKIES)
+              self.class.class_eval("remove_const(:CGI_PARAMS)")
+              self.class.class_eval("remove_const(:CGI_COOKIES)")
             end
           end
         end