replaced sprintf() with snprintf() to prevent possible buffer overflow

* DOCBparser.c HTMLparser.c debugXML.c encoding.c
nanoftp.c nanohttp.c parser.c tree.c uri.c xmlIO.c
xmllint.c xpath.c: replaced sprintf() with snprintf()
to prevent possible buffer overflow (the bug was pointed
out by Anju Premachandran)
diff --git a/HTMLparser.c b/HTMLparser.c
index 82202aa..4a24d68 100644
--- a/HTMLparser.c
+++ b/HTMLparser.c
@@ -1572,7 +1572,7 @@
 	     */
 	    ent = htmlEntityValueLookup(c);
 	    if (ent == NULL) {
-		sprintf(nbuf, "#%u", c);
+		snprintf(nbuf, sizeof(nbuf), "#%u", c);
 		cp = nbuf;
 	    }
 	    else