fix(md5): Add some header file and macro for MD5.

For some old gcc, this is required.

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

eco.h

@@ -13,6 +13,29 @@
 
 #include "helper.h"
 
+#if defined(__linux__) || defined(__CYGWIN__)
+#include <byteswap.h>
+#include <endian.h>
+
+#elif defined(__APPLE__)
+#include <machine/endian.h>
+#include <machine/byte_order.h>
+#elif defined(__FreeBSD__)
+#include <sys/endian.h>
+#else
+#include <machine/endian.h>
+#endif
+
+#ifndef __BYTE_ORDER
+#define __BYTE_ORDER BYTE_ORDER
+#endif
+#ifndef __BIG_ENDIAN
+#define __BIG_ENDIAN BIG_ENDIAN
+#endif
+#ifndef __LITTLE_ENDIAN
+#define __LITTLE_ENDIAN LITTLE_ENDIAN
+#endif
+
 struct eco_context {
     struct ev_loop *loop;
     lua_State *L;