[libxslt] Optimize IS_LEAP

[Nick Wellnhofer <nwellnhof src gnome org>]

commit a2b3d47b3a3215d43149f5d8ab34ebfdecf37b5e
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Wed May 17 21:47:57 2017 +0200

    Optimize IS_LEAP
    
    See http://stackoverflow.com/a/11595914

 libexslt/date.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libexslt/date.c b/libexslt/date.c
index 3af6f7f..625dea6 100644
--- a/libexslt/date.c
+++ b/libexslt/date.c
@@ -148,7 +148,7 @@ struct _exsltDateVal {
 #define VALID_SEC(sec)          ((sec >= 0) && (sec < 60))
 #define VALID_TZO(tzo)          ((tzo > -1440) && (tzo < 1440))
 #define IS_LEAP(y)                                             \
-       (((y % 4 == 0) && (y % 100 != 0)) || (y % 400 == 0))
+       (((y & 3) == 0) && ((y % 25 != 0) || ((y & 15) == 0)))
 
 static const unsigned long daysInMonth[12] =
        { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };