New get_max_points function

Added a new function to allow modules (like the new Advanced Forum) to query for a user's cumulative point earnings. Cumulative points are nice to show a user's long-time contribution to a site in cases when users are allowed to "redeem" their points for rewards (thereby deducting points from their normal total.

This function is almost identical to the already existing get_current_points() function:

function userpoints_get_current_points($uid = 0) {
return (int)db_result(db_query('SELECT points FROM {userpoints} WHERE uid = %d', $uid));

function userpoints_get_max_points($uid = 0) {
return (int)db_result(db_query('SELECT max_points FROM {userpoints} WHERE uid = %d', $uid));