More portable endianness check
https://www.austingroupbugs.net/view.php?id=162#c665

Index: hashtab.c
--- hashtab.c.orig
+++ hashtab.c
@@ -38,7 +38,7 @@ Boston, MA 02110-1301, USA.  */
 #include "hashtab.h"
 
 #include <endian.h>
-#if __BYTE_ORDER == __BIG_ENDIAN
+#if BYTE_ORDER == BIG_ENDIAN
 # define WORDS_BIGENDIAN 1
 #endif