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

src/context_device.cpp

@@ -148,6 +148,12 @@ __device__ void Context::barrier_all() {
   DISPATCH(barrier_all());
 }
 
+__device__ void Context::barrier(rocshmem_team_t team) {
+  ctxStats.incStat(NUM_BARRIER_ALL);
+
+  DISPATCH(barrier(team));
+}
+
 __device__ void Context::sync_all() {
   ctxStats.incStat(NUM_SYNC_ALL);