[libxml2] Fix callback signature in testapi.c

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 00859f9118c59ba419dc08162438a0246af34659
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Sun Nov 12 17:38:08 2017 +0100

    Fix callback signature in testapi.c

 testapi.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/testapi.c b/testapi.c
index 168ceb6..fe42a37 100644
--- a/testapi.c
+++ b/testapi.c
@@ -737,7 +737,8 @@ static void des_xmlSchemaValidCtxtPtr(int no ATTRIBUTE_UNUSED, xmlSchemaValidCtx
 
 #define gen_nb_xmlHashDeallocator 2
 static void
-test_xmlHashDeallocator(void *payload ATTRIBUTE_UNUSED, xmlChar *name ATTRIBUTE_UNUSED) {
+test_xmlHashDeallocator(void *payload ATTRIBUTE_UNUSED,
+                        const xmlChar *name ATTRIBUTE_UNUSED) {
 }
 
 static xmlHashDeallocator gen_xmlHashDeallocator(int no, int nr ATTRIBUTE_UNUSED) {