* cygwin.din: Add sem_close, sem_getvalue, sem_open and sem_timedwait.

* pthread.cc (+mangle_sem_name): New function.
	(sem_open): Ditto.
	(sem_close: Ditto.
	(sem_timedwait): Ditto.
	(sem_getvalue): Ditto.
	* thread.cc (semaphore::semaphore): Rearrange member initialization.
	Use appropriate security attribute for process shared semaphores.
	(semaphore::semaphore): New constructor for named semaphores.
	(semaphore::~semaphore): Care for semaphore name.
	(semaphore::_post): Accomodate failing ReleaseSemaphore. Use value
	returned by ReleaseSemaphore vor currentvalue.
	(semaphore::_getvalue): New method.
	(semaphore::_timedwait): Ditto.
	(semaphore::_fixup_after_fork): Rearrange. Don't fail for process
	shared semaphores.
	(semaphore::open): New method.
	(semaphore::timedwait): Ditto.
	(semaphore::post): Fix return value.  Set errno appropriately.
	(semaphore::getvalue): New method.
	* thread.h (class semaphore): Add prototypes for open, getvalue,
	timedwait, _getvalue, _timedwait.  Add prototypes for new constructor.
	Add name member.
	* include/semaphore.h: Add prototypes for sem_open, sem_close,
	sem_timedwait and sem_getvalue.
	include/cygwin/version.h: Bump API minor number.

winsup/cygwin/cygwin.din

@@ -1122,9 +1122,13 @@ _seed48 = seed48
 seekdir
 _seekdir = seekdir
 _seekdir64 = seekdir64
+sem_close
 sem_destroy
+sem_getvalue
 sem_init
+sem_open
 sem_post
+sem_timedwait
 sem_trywait
 sem_wait
 setbuf