SimpleSAMLPHP custom install autoloader support.

simplesaml-custom-install-autoload.patch

diff --git a/lib/_autoload.php b/lib/_autoload.php
index e44c70f97..75945f742 100644
--- a/lib/_autoload.php
+++ b/lib/_autoload.php
@@ -8,14 +8,21 @@
  * @package SimpleSAMLphp
  */

-// SSP is loaded as a separate project
-if (file_exists(dirname(dirname(__FILE__)) . '/vendor/autoload.php')) {
-    require_once dirname(dirname(__FILE__)) . '/vendor/autoload.php';
-} else {
-    // SSP is loaded as a library
-    if (file_exists(dirname(dirname(__FILE__)) . '/../../autoload.php')) {
-        require_once dirname(dirname(__FILE__)) . '/../../autoload.php';
-    } else {
-        throw new Exception('Unable to load Composer autoloader');
+$directory = dirname(__DIR__);
+$autoload_candidates = [
+    // SSP is loaded as a separate project
+    dirname(__DIR__) . '/vendor/autoload.php',
+    // SSP is loaded as a custom install path in the root.
+    dirname(__DIR__, 2) . '/vendor/autoload.php',
+    // SSP is loaded as a library.
+    dirname(__DIR__, 3) . "/autoload.php",
+];
+
+foreach ($autoload_candidates as $autoload_candidate) {
+    if (file_exists($autoload_candidate)) {
+        require_once $autoload_candidate;
+        return;
     }
 }
+
+throw new Exception('Unable to load Composer autoloader');