BSD compatibility for <machine/endian.h>

Introduce <machine/_endian.h> to let target based customization of
<machine/endian.h> via

 * _LITTLE_ENDIAN,
 * _BIG_ENDIAN,
 * _PDP_ENDIAN, and
 * _BYTE_ORDER.

defines.  Add definitions expected by FreeBSD to
<machine/endian.h> like

 * _QUAD_HIGHWORD,
 * _QUAD_LOWWORD,
 * __bswap16(),
 * __bswap32(),
 * __bswap64(),
 * __htonl(),
 * __htons(),
 * __ntohl(), and
 * __ntohs().

Also, if __BSD_VISIBLE

 * LITTLE_ENDIAN,
 * BIG_ENDIAN,
 * PDP_ENDIAN, and
 * BYTE_ORDER.

Targets that define __machine_host_to_from_network_defined in
<machine/_endian.h> must provide their own implementation of

 * __htonl(),
 * __htons(),
 * __ntohl(), and
 * __ntohs(),

otherwise a default implementation is provided by <machine/endian.h>.
In case of GCC defines to builtins are used.

Signed-off-by: Sebastian Huber <sebastian.huber@embedded-brains.de>

winsup/cygwin/include/machine/_endian.h

@@ -0,0 +1,45 @@
+/* machine/_endian.h
+
+   Copyright 2005, 2010, 2011 Red Hat, Inc.
+
+This file is part of Cygwin.
+
+This software is a copyrighted work licensed under the terms of the
+Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
+details. */
+
+#ifndef __MACHINE_ENDIAN_H__
+#error "must be included via <machine/endian.h>"
+#endif /* !__MACHINE_ENDIAN_H__ */
+
+#include <_ansi.h>
+#include <bits/endian.h>
+
+#define _LITTLE_ENDIAN __LITTLE_ENDIAN
+#define _BIG_ENDIAN    __BIG_ENDIAN
+#define _PDP_ENDIAN    __PDP_ENDIAN
+#define _BYTE_ORDER    __BYTE_ORDER
+
+#define __machine_host_to_from_network_defined
+
+_ELIDABLE_INLINE __uint32_t __ntohl(__uint32_t);
+_ELIDABLE_INLINE __uint16_t __ntohs(__uint16_t);
+
+_ELIDABLE_INLINE __uint32_t
+__ntohl(__uint32_t _x)
+{
+	__asm__("bswap %0" : "=r" (_x) : "0" (_x));
+	return _x;
+}
+
+_ELIDABLE_INLINE __uint16_t
+__ntohs(__uint16_t _x)
+{
+	__asm__("xchgb %b0,%h0"		/* swap bytes		*/
+		: "=Q" (_x)
+		:  "0" (_x));
+	return _x;
+}
+
+#define __htonl(_x) __ntohl(_x)
+#define __htons(_x) __ntohs(_x)