lib/cgi/util.rb: use require

* lib/cgi/util.rb: reverted r65505.  require_relative does not
  work for cgi/escape.so, as extension libraries are placed in
  other directories than ruby libraries.  [Bug #15206]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65511 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/cgi/util.rb

@@ -55,7 +55,7 @@ module CGI::Util
   end
 
   begin
-    require_relative 'escape'
+    require 'cgi/escape'
   rescue LoadError
   end