cleanup cleanup too added xmlNoNetExternalEntityLoader() from xsltproc

* Makefile.am: cleanup
* threads.c: cleanup too
* xmlIO.c include/libxml/xmlIO.h: added xmlNoNetExternalEntityLoader()
  from xsltproc
* include/libxml/tree.h include/libxml/parser.h: trying to break a
  dependancy loop.
Daniel
diff --git a/threads.c b/threads.c
index 4f1b0b8..cde26f4 100644
--- a/threads.c
+++ b/threads.c
@@ -248,6 +248,7 @@
  *									*
  ************************************************************************/
 
+#ifdef LIBXML_THREAD_ENABLED
 /**
  * xmlFreeGlobalState:
  * @state:  a thread global state
@@ -283,6 +284,7 @@
     xmlInitializeGlobalState(gs);
     return (gs);
 }
+#endif /* LIBXML_THREAD_ENABLED */
 
 
 /**