Update databases/openldap to 2.3.11, which is the first "stable" release

Update databases/openldap to 2.3.11, which is the first "stable" release
in the 2.3.x series.  This is a major update over version 2.2.x, and
changes include:

        * Slapd(8) enhancements
            - Updated slapd "overlay" interface, and several
              example (and mostly experimental) overlays.
            - Updated LDAP "sync" Engine with replication support,
              provider now an "overlay"
            - Numerous access control enhancements, including
              experimental "don't disclose on error" capability
            - Configuration backend
        * LDAPv3 extensions, including:
            - LDAP Password Policy
            - LDAP Component Matching (requires OpenLDAP snacc)
            - LDAP Modify Increment