Make hipEvent_t thread safe.

Support re-recording of same event by different threads.

- Add criticalData structure to hipEvent_t, similar to mechanism used
  for streams, contexts, device.  Events are always locked
  after streams to avoid deadlock.
- ihipEvent_t::locked_copyCrit can be used to copy critical state
  including marker.  The critical state in the event can then
  be re-recorded.
- refactor hipEventElapsedTime.  Remmove stale debug code, native signal
  refs.

src/hip_stream.cpp

@@ -93,18 +93,22 @@ hipError_t hipStreamWaitEvent(hipStream_t stream, hipEvent_t event, unsigned int
 
     hipError_t e = hipSuccess;
 
+    auto ecd = event->locked_copyCrit();
+
     if (event == nullptr) {
         e = hipErrorInvalidResourceHandle;
 
-    } else if (event->_state != hipEventStatusUnitialized) {
+    } else if (ecd._state != hipEventStatusUnitialized) {
 
         if (HIP_SYNC_STREAM_WAIT || (HIP_SYNC_NULL_STREAM && (stream == 0))) {
             // conservative wait on host for the specified event to complete:
-            event->locked_waitComplete((event->_flags & hipEventBlockingSync) ? hc::hcWaitModeBlocked : hc::hcWaitModeActive);
+            // return _stream->locked_eventWaitComplete(this, waitMode);
+            //
+            ecd._stream->locked_eventWaitComplete(ecd.marker(), (event->_flags & hipEventBlockingSync) ? hc::hcWaitModeBlocked : hc::hcWaitModeActive);
         } else {
             stream = ihipSyncAndResolveStream(stream);
             // This will use create_blocking_marker to wait on the specified queue.
-            stream->locked_streamWaitEvent(event);
+            stream->locked_streamWaitEvent(ecd);
         }
 
     } // else event not recorded, return immediately and don't create marker.