slightly rework user/operational attributes handling (including fixing a bug in the logic of the previous change to backend_operational()); cleanup; more improvements to slapo-rwm and back-relay

to access the same LDAP* handle.

Coverted LDAP_LOG macro to use subsystem ID int values instead of string values

to allow chasing referrals using the same user's credentials.

Added LDAP_LOG Messages

some memory handling cleanup: check that memory is freed by who allocated it, or at least put a FIXME where not

  - librewrite, for string rewriting; it may be used in back-ldap
    by configuring with '--enable-rewrite'. It must be used in
    back-meta. There's a text file, 'libraries/librewrite/RATIONALE',
    that explains the usage and the features. More comprehensive
    documentation will follow.
  - enhancements of back-ldap (ITS#989,ITS#998,ITS#1002,ITS#1054 and ITS#1137)
    including dn rewriting, a fix to group acl matching and so
  - back-meta: a new backend that proxies a set of remote servers
    by spawning queries. It uses portions of back-ldap and the rewrite
    capabilities of librewrite. It can be compiled by configuring
    with `--enable-ldap --enable-rewrite --enable-meta'.
    There's a text file, 'servers/slapd/back-meta/Documentation', that
    describes the main features and config statements.

Note: someone (Kurt?) should run 'autoconf' and commit 'configure' as
my autoconf version must be different: my configures contain a number
of differences and I didn't feel comfortable in adding them :)

See the Changes file for detailed description.

Replace old Id as needed (back-tcl).
Leave updating of contribWare to contributors (for now).

LDAP_OPT_MATCH_STRING to ldap.h and libldap/options.c.