Merge branch 'wip/carlosg/utf8-strreverse-invalid-writes' into 'master'

gutf8: Assert that written memory stays in bounds

See merge request GNOME/glib!1026

glib/gutf8.c

@@ -1773,6 +1773,7 @@ g_utf8_strreverse (const gchar *str,
     {
       gchar *m, skip = g_utf8_skip[*(guchar*) p];
       r -= skip;
+      g_assert (r >= result);
       for (m = r; skip; skip--)
         *m++ = *p++;
     }