feature: bind user for active_directory auth (#6255)

* feature: bind user for active_directory auth
Optional, allows the use of "remember me", API, and alerting.

* missing global (but still may not be working)

* always return a value from reauthenticate()

* Make sure the ldapbind credentials are correct on reauth.
Do not send output if they are incorrect (use d_echo) this breaks ajax calls, etc.
Add scripts/auth_test.php, to make it easier to debug authentication.

* Refine auth_test.php a bit more
A few small cleanups in other places of the auth

* Add auth_test.php to docs
Some more improvements in the auth_test.php output.

* Update Authentication.md

html/includes/authentication/ad-authorization.inc.php

@@ -54,7 +54,7 @@ function authenticate($username, $password)
 }
 
 
-function reauthenticate()
+function reauthenticate($sess_id, $token)
 {
     // not supported so return 0
     return 0;