small fix from Rob Richards for input filename fixes for --repeat and

* parserInternals.c: small fix from Rob Richards for input filename
* xmllint.c: fixes for --repeat and --memory/--stream for speed tests
* xmlIO: adding a guard in one function
Daniel
diff --git a/xmlIO.c b/xmlIO.c
index 0c40946..c318945 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -1643,6 +1643,8 @@
  */
 void
 xmlFreeParserInputBuffer(xmlParserInputBufferPtr in) {
+    if (in == NULL) return;
+
     if (in->raw) {
         xmlBufferFree(in->raw);
 	in->raw = NULL;