libroot: Implemented pthread barriers

This is an implementation of pthread barriers pursuant to the relevant specification.

Barriers are essentially a special case of conditional variables,
such that all threads waiting on one are woken up when the number of
waiters reaches a number provided at the initialization of the barrier.
In view of that, this implementation mimics the implementation of pthread_cond,
except it is more specialized and self-contained.

Signed-off-by: Jérôme Duval <[email protected]>

headers/private/libroot/pthread_private.h

@@ -37,6 +37,10 @@ typedef struct _pthread_mutexattr {
 	bool		process_shared;
 } pthread_mutexattr;
 
+typedef struct _pthread_barrierattr {
+	bool		process_shared;
+} pthread_barrierattr;
+
 typedef struct _pthread_attr {
 	int32		detach_state;
 	int32		sched_priority;