Fix build on big endian systems by defining MRB_ENDIAN_BIG

Tested on sparc64 by jca@
OK jca@

lang/mruby/Makefile

@@ -1,9 +1,10 @@
-# $OpenBSD: Makefile,v 1.10 2018/12/17 20:28:27 jeremy Exp $
+# $OpenBSD: Makefile,v 1.11 2018/12/20 18:41:45 jeremy Exp $
 
 COMMENT =		lightweight, embeddable implementation of ruby
 
 VERSION =		2.0.0
 DISTNAME =		mruby-${VERSION}
+REVISION =		0
 CATEGORIES =		lang
 HOMEPAGE =		https://github.com/mruby/mruby
 

lang/mruby/patches/patch-include_mrbconf_h

@@ -0,0 +1,24 @@
+$OpenBSD: patch-include_mrbconf_h,v 1.1 2018/12/20 18:41:45 jeremy Exp $
+
+Index: include/mrbconf.h
+--- include/mrbconf.h.orig
++++ include/mrbconf.h
+@@ -7,6 +7,7 @@
+ #ifndef MRUBYCONF_H
+ #define MRUBYCONF_H
+ 
++#include <endian.h>
+ #include <limits.h>
+ #include <stdint.h>
+ 
+@@ -62,7 +63,9 @@
+ //#define MRB_NAN_BOXING
+ 
+ /* define on big endian machines; used by MRB_NAN_BOXING */
+-//#define MRB_ENDIAN_BIG
++#if (BYTE_ORDER == BIG_ENDIAN)
++#define MRB_ENDIAN_BIG
++#endif
+ 
+ /* represent mrb_value as a word (natural unit of data for the processor) */
+ //#define MRB_WORD_BOXING