[PATCH] turn many #if $undefined_string into #ifdef $undefined_string

turn many #if $undefined_string into #ifdef $undefined_string to fix some
warnings after -Wno-def was added to global CFLAGS

Signed-off-by: Olaf Hering <olh@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/drivers/cow.h

@@ -3,10 +3,10 @@
 
 #include <asm/types.h>
 
-#if __BYTE_ORDER == __BIG_ENDIAN
+#if defined(__BIG_ENDIAN)
 # define ntohll(x) (x)
 # define htonll(x) (x)
-#elif __BYTE_ORDER == __LITTLE_ENDIAN
+#elif defined(__LITTLE_ENDIAN)
 # define ntohll(x)  bswap_64(x)
 # define htonll(x)  bswap_64(x)
 #else