[libxml2] timsort.h: support older GCCs

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 9948a9a3558095d91611382671084c60257a6463
Author: Jérôme Duval <jerome duval gmail com>
Date:   Fri Apr 5 06:34:59 2019 +0000

    timsort.h: support older GCCs
    
    cherry-pick upstream pull request: __builtin_clzll isn't available on older GCCs

 timsort.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/timsort.h b/timsort.h
index 0c6346b8..e841bd9c 100644
--- a/timsort.h
+++ b/timsort.h
@@ -74,7 +74,7 @@ typedef unsigned __int64 uint64_t;
 static int compute_minrun(const uint64_t);
 
 #ifndef CLZ
-#ifdef __GNUC__
+#if defined(__GNUC__) && ((__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || (__GNUC__ > 3))
 #define CLZ __builtin_clzll
 #else