Always use application/xml, then the charset is determined by the XML doc

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@3860 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/base.rb

@@ -728,7 +728,7 @@ def render_javascript(javascript, status = nil)
       end
 
       def render_xml(xml, status = nil)
-        @response.headers['Content-Type'] = 'text/xml; charset=UTF-8'
+        @response.headers['Content-Type'] = 'application/xml'
         render_text(xml, status)
       end