Add an ext/hash compatibility layer (just hash_pbkdf2(), for now)
diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index 1f10c45..2bdd764 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -189,6 +189,7 @@
  */
 
 	require_once(BASEPATH.'core/compat/mbstring.php');
+	require_once(BASEPATH.'core/compat/hash.php');
 	require_once(BASEPATH.'core/compat/password.php');
 
 /*