fix an error message added tree2 example from Lucas Brasilino Daniel

* xinclude.c: fix an error message
* doc/examples/*: added tree2 example from Lucas Brasilino
Daniel
diff --git a/xinclude.c b/xinclude.c
index f4d6aee..2ceef0f 100644
--- a/xinclude.c
+++ b/xinclude.c
@@ -1361,7 +1361,7 @@
 	if (xptrctxt == NULL) {
 	    xmlXIncludeErr(ctxt, ctxt->incTab[nr]->ref, 
 	                   XML_XINCLUDE_XPTR_FAILED,
-			   "could create XPointer context\n", NULL);
+			   "could not create XPointer context\n", NULL);
 	    xmlFree(URL);
 	    xmlFree(fragment);
 	    return(-1);