Increase buffer space for port in HTTP redirect support

For https://bugzilla.gnome.org/show_bug.cgi?id=780690

nanohttp.c: the code wrongly assumed a short int port value.
diff --git a/nanohttp.c b/nanohttp.c
index e109ad7..373425d 100644
--- a/nanohttp.c
+++ b/nanohttp.c
@@ -1423,9 +1423,9 @@
     if (ctxt->port != 80) {
 	/* reserve space for ':xxxxx', incl. potential proxy */
 	if (proxy)
-	    blen += 12;
+	    blen += 17;
 	else
-	    blen += 6;
+	    blen += 11;
     }
     bp = (char*)xmlMallocAtomic(blen);
     if ( bp == NULL ) {