Revert "Delete LDAP.php"

This reverts commit 5346182b.

lib/SimpleSAML/Auth/LDAP.php

+<?php
+
+namespace SimpleSAML\Auth;
+
+@trigger_error(
+    sprintf('Using the "SimpleSAML\Auth\LDAP" class is deprecated, use "SimpleSAML\Module\ldap\Auth\Ldap" instead.'),
+    E_USER_DEPRECATED
+);
+
+/**
+ * @deprecated To be removed in 2.0
+ */
+if (class_exists('\SimpleSAML\Module\ldap\Auth\Ldap')) {
+    class LDAP extends \SimpleSAML\Module\ldap\Auth\Ldap
+    {
+        /**
+         * Private constructor restricts instantiation to getInstance().
+         *
+         * @param string $hostname
+         * @param bool $enable_tls
+         * @param bool $debug
+         * @param int $timeout
+         * @param int $port
+         * @param bool $referrals
+         * @psalm-suppress NullArgument
+         */
+        public function __construct(
+            $hostname,
+            $enable_tls = true,
+            $debug = false,
+            $timeout = 0,
+            $port = 389,
+            $referrals = true
+        ) {
+            parent::__construct($hostname, $enable_tls, $debug, $timeout, $port, $referrals);
+        }
+    }
+} else {
+    throw new \Exception('Missing ldap-module');
+}