Run imap_init plugin hook as deprecated hook; set $_SESSION['imap_host'] for backwards compat.

program/include/rcmail.php

@@ -682,13 +682,12 @@ class rcmail
       $options['port']     = $_SESSION['storage_port'];
       $options['ssl']      = $_SESSION['storage_ssl'];
       $options['password'] = $this->decrypt($_SESSION['password']);
+      // set 'imap_host' for backwards compatibility
+      $_SESSION[$driver.'_host'] = &$_SESSION['storage_host'];
     }
 
     $options = $this->plugins->exec_hook("storage_init", $options);
 
-    // for backward compat. (deprecated, to be removed)
-    $options = $this->plugins->exec_hook("imap_init", $options);
-
     $this->storage->set_options($options);
     $this->set_storage_prop();
   }

program/include/rcube_plugin_api.php

@@ -71,6 +71,7 @@ class rcube_plugin_api
     'delete_identity'   => 'identity_delete',
     'save_identity'     => 'identity_update',
     'identity_save'     => 'identity_update',
+    'imap_init'         => 'storage_init',
   );
 
   /**