Do not pass timelimit and deref settings to ldap_search. These values
should be set globally via ldap_set_option() instead (as we do for
deref).

This reverts commit 37764cbb.

adLDAP renamed the ad_username and ad_password to admin_username
admin_password recently. this makes our backend recognize the old
settings

again)

canDo getUsers to false when unavailable

This reverts commit ba09710a.

Conflicts:
	lib/plugins/authad/lang/de/settings.php

Before this fix the debug parameter always prevent the GIF from being
sent even though no actual debug information was returned unless the
allowdebug configuration option was set. Now the GIF is only disabled if
debugging is actually allowed.

de/de-informal: config plugin - Clean up the TOC in the configuration page / No need to add "Konfiguration" or "Plugin" to every element if the heading tells you that.