Vtiger.php language pack / app.translate problem still exists after nearly 5 years.

I'm creating an extension module. In a Javascript class I need to translate a string but I cannot because of this bug.

See http://lists.vtigercrm.com/pipermail/vtigercrm-developers/2015-March/031765.html
and http://trac.vtiger.com/cgi-bin/trac.cgi/ticket/8562

(I have no easy way round this problem by translating it using ajax or in a template file)