Safer ABI for O_TMPFILE

[suggested by Rasmus Villemoes] make O_DIRECTORY | O_RDWR part of O_TMPFILE;
that will fail on old kernels in a lot more cases than what I came up with.
And make sure O_CREAT doesn't get there...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/alpha/include/uapi/asm/fcntl.h

@@ -32,7 +32,7 @@
 #define O_SYNC		(__O_SYNC|O_DSYNC)
 
 #define O_PATH		040000000
-#define O_TMPFILE	0100000000
+#define __O_TMPFILE	0100000000
 
 #define F_GETLK		7
 #define F_SETLK		8