* 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.
