timerfd: update flags decoding

The current code only decodes TFD_TIMER_ABSTIME when the kernel has
a bunch of newer flags.  We have to handle fallbacks for all of them
since the kernel doesn't currently export things to userspace.

* time.c: Include fcntl.h for O_* defines.
(TFD_TIMER_ABSTIME): Move to xlat/timerfdflags.in.
* xlat/timerfdflags.in: Add more definitions.

time.c

@@ -28,6 +28,7 @@
  */
 
 #include "defs.h"
+#include <fcntl.h>
 #include <linux/version.h>
 #include <sys/timex.h>
 #include <linux/ioctl.h>
@@ -809,10 +810,6 @@ rtc_ioctl(struct tcb *tcp, long code, long arg)
 	return 1;
 }
 
-#ifndef TFD_TIMER_ABSTIME
-#define TFD_TIMER_ABSTIME (1 << 0)
-#endif
-
 #include "xlat/timerfdflags.h"
 
 int

xlat/timerfdflags.in

@@ -1 +1,21 @@
+/* The Linux userspace headers didn't export these for a long time. */
+
+#ifndef TFD_TIMER_ABSTIME
+# define TFD_TIMER_ABSTIME (1 << 0)
+#endif
 TFD_TIMER_ABSTIME
+
+#ifndef TFD_TIMER_CANCEL_ON_SET
+# define TFD_TIMER_CANCEL_ON_SET (1 << 1)
+#endif
+TFD_TIMER_CANCEL_ON_SET
+
+#ifndef TFD_CLOEXEC
+# define TFD_CLOEXEC O_CLOEXEC
+#endif
+TFD_CLOEXEC
+
+#ifndef TFD_NONBLOCK
+# define TFD_NONBLOCK O_NONBLOCK
+#endif
+TFD_NONBLOCK