[libxml2] Work around buggy ceil() function on AIX

[Nick Wellnhofer <nwellnhof src gnome org>]

commit b17e3d1c2b6a6d4f3d365faa9908d2c91ca32420
Author: Daniel Richard G <skunk iSKUNK ORG>
Date:   Thu Aug 1 15:04:16 2019 +0200

    Work around buggy ceil() function on AIX
    
    AIX has a buggy ceil() function that does not handle negative-zero
    correctly.
    
    Closes #79.

 xpath.c | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/xpath.c b/xpath.c
index 4734ecc4..65a9f09e 100644
--- a/xpath.c
+++ b/xpath.c
@@ -9584,7 +9584,12 @@ xmlXPathCeilingFunction(xmlXPathParserContextPtr ctxt, int nargs) {
     CAST_TO_NUMBER;
     CHECK_TYPE(XPATH_NUMBER);
 
+#ifdef _AIX
+    /* Work around buggy ceil() function on AIX */
+    ctxt->value->floatval = copysign(ceil(ctxt->value->floatval), ctxt->value->floatval);
+#else
     ctxt->value->floatval = ceil(ctxt->value->floatval);
+#endif
 }
 
 /**