add rocshmem_barrier() (#61)

* add team-barrier implementation

add a team-barrier API and implementation in the IPC and RO conduit.
Clean up some of the logic in the RO Conduit to distinguish between
sync, sync_all, barrier, and barrier_all.

* add team_barrier_tests to functional tests

include/rocshmem/rocshmem.hpp

@@ -465,6 +465,16 @@ __device__ ATTR_NO_INLINE void rocshmem_ctx_wg_barrier_all(
 
 __device__ ATTR_NO_INLINE void rocshmem_wg_barrier_all();
 
+/**
+ * @brief perform a collective barrier between all PEs in the team.
+ * The caller is blocked until the barrier is resolved.
+ *
+ * @param[in] team    The team on which to perform barrier synchronization
+ *
+ * @return void
+ */
+__device__ void rocshmem_barrier(rocshmem_team_t);
+
 /**
  * @brief registers the arrival of a PE at a barrier.
  * The caller is blocked until the synchronization is resolved.