Merge pull request #2455 from vijaydev/patch-7

Edit changelog to mention about x_sendfile_header default change

actionpack/CHANGELOG

@@ -30,6 +30,8 @@
 
 *Rails 3.1.0 (unreleased)*
 
+* x_sendfile_header now defaults to nil and config/environments/production.rb doesn't set a particular value for it. This allows servers to set it through X-Sendfile-Type. [Santiago Pastorino]
+
 * The submit form helper does not generate an id "object_name_id" anymore. [fbrusatti]
 
 * Make sure respond_with with :js tries to render a template in all cases [José Valim]