* lib: try to reopen database when it got updated from the outside (for guile)

lib/mu-msg-iter.h

@@ -48,13 +48,16 @@ typedef struct _MuMsgIter MuMsgIter;
  * @param sorting field when using threads; note, when 'threads' is
  * FALSE, this should be MU_MSG_FIELD_ID_NONE
  * @param if TRUE, revert the sorting order
+ * @param err receives error information. if the error is MU_ERROR_XAPIAN_MODIFIED,
+ * the database should be reloaded.
  *
  * @return a new MuMsgIter, or NULL in case of error
  */
 MuMsgIter *mu_msg_iter_new (XapianEnquire *enq,
 			    size_t batchsize, gboolean threads,
 			    MuMsgFieldId threadsortfield,
-			    gboolean revert) G_GNUC_WARN_UNUSED_RESULT;
+			    gboolean revert,
+			    GError **err) G_GNUC_WARN_UNUSED_RESULT;
 
 /**
  * get the next message (which you got from