Provide a token for the site's base URL

Hi,

my multilanguage site is configured to show language prefixes on paths, but didn't expect to see the language prefix in the value of the[site-url] token too, and it seems it is not possible to pass options for the global tokens either in token_token_values().

To prevent the language prefix from showing in the url, we can use this snippet

$values['site-url']     = url('<front>', array('absolute' => TRUE, 'language' => ''));

Let me know if the change looks OK to you, in this case I can send a proper patch.

Thanks,
Antonio