[vala] libxml-2.0: Fix header of XPath.Context.register_ns()

[Rico Tzschichholz <ricotz src gnome org>]

commit 4a2e3212d2fe502b44d4d299fff33c6060d840f5
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sat Oct 7 12:53:12 2017 +0200

    libxml-2.0: Fix header of XPath.Context.register_ns()

 vapi/libxml-2.0.vapi |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/vapi/libxml-2.0.vapi b/vapi/libxml-2.0.vapi
index 273b0a5..12a2d78 100644
--- a/vapi/libxml-2.0.vapi
+++ b/vapi/libxml-2.0.vapi
@@ -1554,7 +1554,7 @@ namespace Xml {
                        [CCode (cname = "xmlXPathEvalExpression", instance_pos = -1)]
                        public Object* eval_expression ([CCode (type = "xmlChar*")] string str);
 
-                       [CCode (cname = "xmlXPathRegisterNs")]
+                       [CCode (cname = "xmlXPathRegisterNs", cheader_filename = "libxml/xpathInternals.h")]
                        public int register_ns ([CCode (type = "xmlChar*")] string prefix, [CCode (type = 
"xmlChar*")] string ns_uri);
 
                        [CCode (cname = "xmlXPathNewContext")]