robert pointed out a loop error in callback cleanups Daniel

* xmlIO.c: robert pointed out a loop error in callback cleanups
Daniel
diff --git a/xmlIO.c b/xmlIO.c
index 7fd101c..b9b9ae6 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -136,7 +136,7 @@
     if (!xmlInputCallbackInitialized)
         return;
 
-    for (i = xmlInputCallbackNr - 1; i <= 0; i--) {
+    for (i = xmlInputCallbackNr - 1; i >= 0; i--) {
         xmlInputCallbackTable[i].matchcallback = NULL;
         xmlInputCallbackTable[i].opencallback = NULL;
         xmlInputCallbackTable[i].readcallback = NULL;
@@ -161,7 +161,7 @@
     if (!xmlOutputCallbackInitialized)
         return;
 
-    for (i = xmlOutputCallbackNr - 1; i <= 0; i--) {
+    for (i = xmlOutputCallbackNr - 1; i >= 0; i--) {
         xmlOutputCallbackTable[i].matchcallback = NULL;
         xmlOutputCallbackTable[i].opencallback = NULL;
         xmlOutputCallbackTable[i].writecallback = NULL;