Cygwin: implement extensible clock interface

- Drop hires_[nm]s clocks, rename hires.h to clock.h.

- Implement clk_t class as an extensible clock class in new file clock.cc.

- Introduce get_clock(clock_id) returning a pointer to the clk_t instance
  for clock_id.  Provide the following methods along the lines of the former
  hires classes:

	void		clk_t::nsecs (struct timespec *);
	ULONGLONG	clk_t::nsecs ();
	LONGLONG	clk_t::usecs ();
	LONGLONG	clk_t::msecs ();
	void 		clk_t::resolution (struct timespec *);

- Add CLOCK_REALTIME_COARSE, CLOCK_MONOTONIC_RAW, CLOCK_MONOTONIC_COARSE
  and CLOCK_BOOTTIME clocks.

- Allow clock_nanosleep, pthread_condattr_setclock and timer_create to use
  all new clocks (both clocks should be usable with a small tweak, though).

- Bump DLL major version to 2.12.

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

winsup/cygwin/signal.cc

@@ -76,16 +76,9 @@ clock_nanosleep (clockid_t clk_id, int flags, const struct timespec *rqtp,
   /* support for CPU-time clocks is optional */
   if (CLOCKID_IS_PROCESS (clk_id) || CLOCKID_IS_THREAD (clk_id))
     return ENOTSUP;
-
-  switch (clk_id)
-    {
-    case CLOCK_REALTIME:
-    case CLOCK_MONOTONIC:
-      break;
-    default:
-      /* unknown or illegal clock ID */
-      return EINVAL;
-    }
+  /* All other valid clocks are valid */
+  if (clk_id >= MAX_CLOCKS)
+    return EINVAL;
 
   LARGE_INTEGER timeout;
 
@@ -103,14 +96,18 @@ clock_nanosleep (clockid_t clk_id, int flags, const struct timespec *rqtp,
 	  || (tp.tv_sec == rqtp->tv_sec && tp.tv_nsec > rqtp->tv_nsec))
 	return 0;
 
-      if (clk_id == CLOCK_REALTIME)
-	timeout.QuadPart += FACTOR;
-      else
+      switch (clk_id)
 	{
+	case CLOCK_REALTIME_COARSE:
+	case CLOCK_REALTIME:
+	  timeout.QuadPart += FACTOR;
+	  break;
+	default:
 	  /* other clocks need to be handled with a relative timeout */
 	  timeout.QuadPart -= tp.tv_sec * NS100PERSEC
 			      + tp.tv_nsec / (NSPERSEC/NS100PERSEC);
 	  timeout.QuadPart *= -1LL;
+	  break;
 	}
     }
   else /* !abstime */