Chasing dead assignments reported by clang-scan

* SAX2.c dict.c error.c hash.c nanohttp.c parser.c python/libxml.c
  relaxng.c runtest.c tree.c valid.c xinclude.c xmlregexp.c xmlsave.c
  xmlschemas.c xpath.c xpointer.c: mostly removing unneded affectations,
  but this led to a few real bugs and some part not yet understood
  (relaxng/interleave)
diff --git a/relaxng.c b/relaxng.c
index 5146d9d..0122d57 100644
--- a/relaxng.c
+++ b/relaxng.c
@@ -6517,6 +6517,10 @@
         if (ptype == XML_RELAXNG_GROUP) {
             val = xmlRelaxNGGroupContentType(val, ret);
         } else if (ptype == XML_RELAXNG_INTERLEAVE) {
+            /*
+             * TODO: scan complain that tmp is never used, seems on purpose
+             *       need double-checking
+             */
             tmp = xmlRelaxNGGroupContentType(val, ret);
             if (tmp != XML_RELAXNG_CONTENT_ERROR)
                 tmp = xmlRelaxNGMaxContentType(val, ret);