Use config.h's WORDS_BIGENDIAN.

src/futil.c

@@ -143,15 +143,8 @@ static char *copyright = "Copyright (C) 1992 The Geometry Center";
 #undef isspace
 #undef isalnum
 
-#ifdef __BYTE_ORDER
-# if __BYTE_ORDER == __BIG_ENDIAN
-#  define AM_BIG_ENDIAN 1
-# else
-#  define AM_BIG_ENDIAN 0
-# endif
-#endif
 
-#ifdef WORDS_BIGENDIAN
+#if WORDS_BIGENDIAN
 # define AM_BIG_ENDIAN  WORDS_BIGENDIAN
 #else
    /* Speedy binary I/O if the machine is known to be big-endian */