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/strace.cc

@@ -82,8 +82,14 @@ strace::dll_info ()
 int
 strace::microseconds ()
 {
-  static hires_ns now NO_COPY;
-  return (int) now.usecs ();
+  /* Need a local clock instance because this function is called before
+     the global constructors of the inferior process have been called. */
+  static clk_monotonic_t clock_monotonic;
+  static LONGLONG process_start NO_COPY;
+
+  if (!process_start)
+    process_start = clock_monotonic.usecs ();
+  return (int) (clock_monotonic.usecs () - process_start);
 }
 
 static int __stdcall