Fix SXEmacs semaphores so that they deal with spurius pthreads conditional variable...

Fix SXEmacs semaphores so that they deal with spurius pthreads conditional variable wakeups

	* src/semaphore.h (struct sxe_semaphore_s): add a generation count
	* src/semaphore.h (struct sxe_msemaphore_s): ditto

	* src/semaphore.h (sxe_msemaphore_init): initialize generation
	* src/semaphore.h (sxe_semaphore_init): ditto

	* src/semaphore.h (sxe_msemaphore_trigger): increment generation before signal
	* src/semaphore.h (sxe_msemaphore_trigger): ditto
	* src/semaphore.h (sxe_msemaphore_trigger_all): ditto
	* src/semaphore.h (sxe_msemaphore_trigger_all): ditto

	* src/semaphore.h (sxe_msemaphore_synchronise): Wait again if
	generation is still the same (ie no signal occurred).

	* src/semaphore.h (sxe_msemaphore_synchronise): ditto.

Signed-off-by: Nelson Ferreira <nelson.ferreira@ieee.org>