This reverts commits 22b0995c and
dbdc867b.

RT::Authen::ExternalAuth is switching to ->Update as well, which lets us
use ->Update here without the waffling problem described by 22b0995c.
Using more core code is better.

Update method does s/\r\n/\n/g on values. This change
of values is not visible, but if combined with ExternalAuth
can result in regular change of a field back and forth.

The original code from 56d0d416 only stands a chance at working on RT
3.6.  RT 3.8 and 4.0 use the modern config handling and call
RT->Config->Get('Plugins') to load plugins.  Get() doesn't read values
from the RT:: namespace; it uses a secondary store which we never
affected.  By calling Set() ourselves we ensure the config is properly
updated and seen by the subsequent RT::Init() call.

It's not easy to exclude numeric users/groups with an LDAP filter,
leaving no way of acknowledging and suppressing the warning.  Rather
than add an option, just lower the log level.

While debugging it's helpful to see what was skipped, but under normal
usage (i.e. from cron), you want to ensure you see meaningful errors and
warnings not the same ones every night.

You may want to update just one or the other manually while between
cronjobs.

Filtering on (dn=...) is invalid because DN isn't an attribute.
Therefore if DN is what we need to search on, use the member's DN as the
search base and the standard user filter.  Only if we're searching on an
attribute do we now use the standard user base and an extended user
filter.

This lets you import a lot more of your LDAP information into RT, which
can be especially helpful with custom user/requestor displays on
tickets.

Note that the prefix is UserCF. not CF. as that's already used for
populating Custom Field Values (not _Object_ Custom Field Values).

Moved install instructions to INSTALL.

README is now generated from the pod via ReadmeFromPod.

Some more updates to pod in main file.

Added a feature to allow you to use a regex to match an LDAP member
field. But upon further review, I don't think it would ever be
needed unless someone's LDAP was really mis-configured. So this
commit is for posterity only.
(cherry picked from commit f5b2b5c7d0a02577f36782bebfdc5ff2082f9951)

Avoids extra user canonicalization calls which often go back to an
external info source, such as the same LDAP directory we just fetched
the info from.

This does mean you can no longer implement configurations where you
import from LDAP and use ExternalAuth to fetch different user info from
another source, but I think that's an acceptable tradeoff.

Either from the $PERL environment variable or the perl that Makefile.PL
is run with.

Adds $LDAPSizeLimit which controls the page size requested by the
importer.  This lets us work with servers where the result set size
limit can't be increased.  If $LDAPSizeLimit is 0 or unset, no paging is used.

API change: _run_search now returns an array of Net::LDAP::Entry objects
instead of a Net::LDAP::Search object.