implement a cache for dn2uid() lookups that saves some time doing LDAP searches for groups with a lot of members, based on a patch by Petter Reinholdtsen <pere@hungry.com>
implement a cache for dn2uid() lookups that saves some time doing LDAP searches for groups with a lot of members, based on a patch by Petter Reinholdtsen <pere@hungry.com>

git-svn-id: 42347dce00c86f9aec5f22b61aa49406f8a6f818@722 ef36b2f9-881f-0410-afb5-c4e39611909c

arthurdejong/nss-pam-ldapd,arthurdejong/nss-pam-ldapd,arthurdejong/nss-pam-ldapd