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/aio.cc

@@ -7,7 +7,6 @@ Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
 details. */
 
 #include "winsup.h"
-#include "hires.h"
 #include "path.h"
 #include "fhandler.h"
 #include "dtable.h"
@@ -803,12 +802,12 @@ retry:
       return -1;
     }
 
-  time0 = ntod.nsecs ();
+  time0 = get_clock (CLOCK_MONOTONIC)->nsecs ();
   /* Note wait below is abortable even w/ empty sigmask and infinite timeout */
   res = sigtimedwait (&sigmask, &si, timeout ? &to : NULL);
   if (res == -1)
     return -1; /* Return with errno set by failed sigtimedwait() */
-  time1 = ntod.nsecs ();
+  time1 = get_clock (CLOCK_MONOTONIC)->nsecs ();
 
   /* Adjust timeout to account for time just waited */
   time1 -= time0;