- add iilBasicHeader alias for rcube_mail_header class, needed by messages cached in previous versions (#1486602)

program/include/rcube_imap_generic.php

@@ -65,6 +65,10 @@ class rcube_mail_header
 	public $others = array();
 }
 
+// For backward compatibility with cached messages (#1486602)
+class iilBasicHeader extends rcube_mail_header
+{
+}
 
 class rcube_imap_generic
 {