Proxy URL doesn't work if a language path prefix is used

Problem/Motivation

If the site is multilingual and uses the path prefix, the code that makes sure the URL is absolute adds the path prefix, but since it actually calls directly a script and not a Drupal callback, the language makes the URL invalid.

Proposed resolution

My first try would be to add the 'language' => LANGUAGE_NONE item to the array of options passed to url(). I'm not sure if this would have any effect on multilingual sites using domains for language detection.