Get a user's all groups

Hi,

apr_uid_current() can retur the user id and primary group id of a user. Is
there a way to find out if a user also has secondary groups (something
similar to getgrouplist(3)?

The Subversion project has some bug reports where a user has R/W access to
a certain file via a secondary group, but APR doesn't pick up the secondary
groups and thus we don't think the user has R/W access. I'd like to improve
this by also considering all secondary groups.

Kind regards,
Daniel Sahlberg