[libxslt] Fix XPath callback signatures

[Nick Wellnhofer <nwellnhof src gnome org>]

commit c32117ce26dd21c0e05439744e05573b4cc51f50
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Wed Nov 29 15:54:34 2017 +0100

    Fix XPath callback signatures

 libxslt/functions.c |    3 ++-
 libxslt/functions.h |    4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/libxslt/functions.c b/libxslt/functions.c
index 43d82f6..a21eedc 100644
--- a/libxslt/functions.c
+++ b/libxslt/functions.c
@@ -65,8 +65,9 @@
  * Returns the callback function or NULL if not found
  */
 xmlXPathFunction
-xsltXPathFunctionLookup (xmlXPathContextPtr ctxt,
+xsltXPathFunctionLookup (void *vctxt,
                         const xmlChar *name, const xmlChar *ns_uri) {
+    xmlXPathContextPtr ctxt = (xmlXPathContextPtr) vctxt;
     xmlXPathFunction ret;
 
     if ((ctxt == NULL) || (name == NULL) || (ns_uri == NULL))
diff --git a/libxslt/functions.h b/libxslt/functions.h
index e0e0bf9..5455b7f 100644
--- a/libxslt/functions.h
+++ b/libxslt/functions.h
@@ -26,11 +26,11 @@ extern "C" {
  */
 #define XSLT_REGISTER_FUNCTION_LOOKUP(ctxt)                    \
     xmlXPathRegisterFuncLookup((ctxt)->xpathCtxt,              \
-       (xmlXPathFuncLookupFunc) xsltXPathFunctionLookup,       \
+       xsltXPathFunctionLookup,                                \
        (void *)(ctxt->xpathCtxt));
 
 XSLTPUBFUN xmlXPathFunction XSLTCALL
-       xsltXPathFunctionLookup         (xmlXPathContextPtr ctxt,
+       xsltXPathFunctionLookup         (void *vctxt,
                                         const xmlChar *name,
                                         const xmlChar *ns_uri);