UAPI: fix endianness conditionals in linux/acct.h

In the UAPI header files, __BIG_ENDIAN and __LITTLE_ENDIAN must be
compared against __BYTE_ORDER in preprocessor conditionals where these are
exposed to userspace (that is they're not inside __KERNEL__ conditionals).

However, in the main kernel the norm is to check for
"defined(__XXX_ENDIAN)" rather than comparing against __BYTE_ORDER and
this has incorrectly leaked into the userspace headers.

The definition of ACCT_BYTEORDER in linux/acct.h is wrong in this way.
Note that userspace will likely interpret this incorrectly as the
big-endian variant on little-endian machines - depending on header
inclusion order.

[!!!] NOTE [!!!]  This patch may adversely change the userspace API.  It might
be better to fix the value of ACCT_BYTEORDER.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/uapi/linux/acct.h

@@ -107,10 +107,12 @@ struct acct_v3
 #define ACORE		0x08	/* ... dumped core */
 #define AXSIG		0x10	/* ... was killed by a signal */
 
-#ifdef __BIG_ENDIAN
+#if defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : defined(__BIG_ENDIAN)
 #define ACCT_BYTEORDER	0x80	/* accounting file is big endian */
-#else
+#elif defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : defined(__LITTLE_ENDIAN)
 #define ACCT_BYTEORDER	0x00	/* accounting file is little endian */
+#else
+#error unspecified endianness
 #endif
 
 #ifndef __KERNEL__