small portability glitch fixed. Daniel

* xmlIO.c: small portability glitch fixed.
Daniel
diff --git a/xmlIO.c b/xmlIO.c
index 0b8927a..1234140 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -12,7 +12,10 @@
 #include "libxml.h"
 
 #include <string.h>
+#ifdef HAVE_ERRNO_H
 #include <errno.h>
+#endif
+
 
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>