update guard, add win32 support for endian.h

Thanks to Jonas 'Sortie' Termansen for pointing the guard inconsistency out.

ok beck@

include/machine/endian.h

@@ -1,14 +1,30 @@
-#ifndef _COMPAT_BYTE_ORDER_H_
-#define _COMPAT_BYTE_ORDER_H_
+#ifndef LIBCRYPTOCOMPAT_BYTE_ORDER_H_
+#define LIBCRYPTOCOMPAT_BYTE_ORDER_H_
 
-#ifdef __linux__
-#include <endian.h>
+#if defined(__WIN32)
+
+#define LITTLE_ENDIAN  1234
+#define BIG_ENDIAN 4321
+#define PDP_ENDIAN	3412
+
+/*
+ * Use GCC and Visual Studio compiler defines to determine endian.
+ */
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define BYTE_ORDER LITTLE_ENDIAN
 #else
-#ifdef __sun
+#define BYTE_ORDER BIG_ENDIAN
+#endif
+
+#elif defined(__linux__)
+#include <endian.h>
+
+#elif defined(__sun)
 #include <arpa/nameser_compat.h>
+
 #else
 #include_next <machine/endian.h>
-#endif
+
 #endif
 
 #endif