retain additional query variables in url.php

When using hook_civicrm_alterMailParams to add additional query variables to links with click through enabled, the links will look like

http://www.example.com/sites/all/modules/civicrm/extern/url.php?qid=xxx&u=xxx&additional_param1=A&additional_param2=B,

When the url redirect to the original email message occurs, the additional query variables are dropped.

url.php should be rewritten to retain the additional query variables when redirecting since making hook_alterMailParams fire before the url rewrite occurs is not a viable options.

The fix will be committed to 3.3 branch