cleanup patch from Anthony Jones fix the headers to avoid in make scan

* SAX.c: cleanup patch from Anthony Jones
* doc/Makefile.am: fix the headers to avoid in make scan
* parserInternals.c xpath.c include/libxml/*.h: cleanup of the
  includes, * vs Ptr and general cleanup
* parsedecl.py: first version of a script to extract the
  module interfaces, the goal will be to provide .decl or XML
  specification of the interfaces to build wrappers.
Daniel
diff --git a/xpath.c b/xpath.c
index 8e3adb6..9b07ce6 100644
--- a/xpath.c
+++ b/xpath.c
@@ -2291,9 +2291,10 @@
 
     if (ctxt->funcLookupFunc != NULL) {
 	xmlXPathFunction ret;
+	xmlXPathFuncLookupFunc *f;
 
-	ret = ((xmlXPathFuncLookupFunc) ctxt->funcLookupFunc)
-	    (ctxt->funcLookupData, name, NULL);
+	f = (xmlXPathFuncLookupFunc *) ctxt->funcLookupFunc;
+	ret = f(ctxt->funcLookupData, name, NULL);
 	if (ret != NULL)
 	    return(ret);
     }
@@ -2321,9 +2322,10 @@
 
     if (ctxt->funcLookupFunc != NULL) {
 	xmlXPathFunction ret;
+	xmlXPathFuncLookupFunc *f;
 
-	ret = ((xmlXPathFuncLookupFunc) ctxt->funcLookupFunc)
-	    (ctxt->funcLookupData, name, ns_uri);
+	f = (xmlXPathFuncLookupFunc *) ctxt->funcLookupFunc;
+	ret = f(ctxt->funcLookupData, name, ns_uri);
 	if (ret != NULL)
 	    return(ret);
     }