i18n_menu support

Deco does not use blocks for the primary-links, it may be a problem in itself but it's not the subject here.
Deco currently use menu_tree in template.php in order to provide the main-menu.
But if one uses i18n, every single item will be printed while you only want those of the requested language.
That's why i18n_menu_translated_tree exists. It's called automatically for blocks but should be handled manually otherwise.