Add back compile-time test for s390x when determining endianness.
diff --git a/src/farmhash.h b/src/farmhash.h
index 95388de..f90ca17 100644
--- a/src/farmhash.h
+++ b/src/farmhash.h
@@ -312,7 +312,7 @@
       #define FARMHASH_BIG_ENDIAN
     #endif
   #endif
-#elif defined(__OpenBSD__) || defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__)
+#elif defined(__OpenBSD__) || defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__) || defined(__s390x__)
   #include <sys/endian.h>
   #if BYTE_ORDER == BIG_ENDIAN
     #if !defined(FARMHASH_BIG_ENDIAN)