Add ldap_control_assertion to create assertion controls.
Add optional control parameters for add/modify/replace/delete.

Currently only one LDAPControl (per server/client) can be specified.
Add tests for ldap_control_assertion
Implement session tracking control
Add functionality to pass single controls or a list of controls as server controls in functions using php_ldap_do_modify
Factor out the ldap controls handling code.

And reuse it for client controls as well.