558452 fight with reg test and error report

* relaxng.c: tiny fix and provide more context on some errors
* result/relaxng/558452_0* test/relaxng/558452*: add some regression
  tests for the bugs
* Makefile.am runtest.c: fight with the fact streaming error messages
  can differ due to missing node context
diff --git a/runtest.c b/runtest.c
index c821786..1d64695 100644
--- a/runtest.c
+++ b/runtest.c
@@ -3257,7 +3257,8 @@
      * hack is also done in the Makefile
      */
     if ((!strcmp(prefix, "tutor10_1")) || (!strcmp(prefix, "tutor10_2")) ||
-        (!strcmp(prefix, "tutor3_2")) || (!strcmp(prefix, "307377")))
+        (!strcmp(prefix, "tutor3_2")) || (!strcmp(prefix, "307377")) ||
+        (!strcmp(prefix, "tutor8_2")))
 	disable_err = 1;
 
     snprintf(pattern, 499, "./test/relaxng/%s_?.xml", prefix);