LJ::fill_groups_xmlrpc — Fills a hashref (presumably to be sent to an XMLRPC client, EG fotobilder) with user friend group information
u. A hashref of a row from the user table, sometimes called a "user object". Although only initially a row from the user table, gets a lot of tacked onto it from various other LJ API functions.
ret. a response hashref to fill with friend group data
undef if called incorrectly, 1 otherwise