Fix large parse of file from memory

https://bugzilla.redhat.com/show_bug.cgi?id=862969
The new code trying to detect excessive input lookup would
just get wrong sometimes in the case of very large file parsed
directly from memory.
diff --git a/xmlIO.c b/xmlIO.c
index f8f438b..44254e4 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -800,7 +800,7 @@
     return 1;
 }
 
-static int
+int
 xmlNop(void) {
     return(0);
 }