Cygwin: timers: implement timerfd

First cut of a timerfd implementation.

Still TODO:
- fork/exec semantics
- timerfd_settime TFD_TIMER_CANCEL_ON_SET flag
- ioctl(TFD_IOC_SET_TICKS)
- bug fixes

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/include/sys/timerfd.h

@@ -0,0 +1,45 @@
+/* sys/timerfd.h: define timerfd_create(2) and friends
+
+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	_SYS_TIMERFD_H
+#define	_SYS_TIMERFD_H
+
+#include <time.h>
+#include <sys/_default_fcntl.h>
+#include <asm/socket.h>
+
+enum
+{
+  /* timerfd_create */
+  TFD_CLOEXEC = O_CLOEXEC,
+  TFD_NONBLOCK = O_NONBLOCK,
+  /* timerfd_settime */
+  TFD_TIMER_ABSTIME = TIMER_ABSTIME,
+  TFD_TIMER_CANCEL_ON_SET = (TIMER_ABSTIME << 1)
+};
+#define TFD_CLOEXEC TFD_CLOEXEC
+#define TFD_NONBLOCK TFD_NONBLOCK
+#define TFD_TIMER_ABSTIME TFD_TIMER_ABSTIME
+#define TFD_TIMER_CANCEL_ON_SET TFD_TIMER_CANCEL_ON_SET
+
+#define TFD_IOC_SET_TICKS	_IOW('T', 0, __uint64_t)
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern int timerfd_create (clockid_t, int);
+extern int timerfd_settime (int, int, const struct itimerspec *,
+			    struct itimerspec *);
+extern int timerfd_gettime (int, struct itimerspec *);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _SYS_TIMERFD_H */