This caused find_domain() with memcache enabled to return different result
than without the cache. Which in result led to wrong domain_root_dn() result.
And that caused webadmin unuseable.

They are still allowed in debug messages.

Roundcube does not set this value. Unset option didn't allow to
detect vlv indexes.
Also changed the way options are handled in constructor. I saw no
reason why they should not override already set options.

Additionally:
- use get_entry() instead of search() where appropriate
- fetch vendorname and supportedcontrol in a single ldap_read() call
- make some private methods protected, cleanup code

1. Prevent from errors when the host is configured e.g. with ldap:// prefix
2. Use sys_get_temp_dir() to get the system tmp directory

This reverts commit 0ba431be.

Summary:
This change will allow the package to be submitted to packagist.org
for easy installation via Composer.

Reviewers: vanmeeuwen, machniak

Reviewed By: machniak

Subscribers: bruederli

Differential Revision: https://git.kolab.org/D121