[Compass Core] A new helper function stylesheet_url(path) can now be used to refer to assets that are relative to the css directory.

lib/compass/configuration.rb

@@ -144,8 +144,9 @@ module Compass
       end
     end
 
-    def mk_http_path(path)
+    def root_relative(path)
-      hp = http_path[0..-2] if http_path[-1..-1] == "/"
+      hp = http_path || default_http_path
+      hp = hp[0..-2] if hp[-1..-1] == "/"
       "#{hp}/#{path}"
     end