Implement clEnqueueMarker and clEnqueueBarrier.

Implement clEnqueueMarker and clEnqueueBarrier.

Add some event info to cl_command_queue.
One is non-complete user events, used to block marker event and barrier.
After these events become CL_COMPLETE, the events blocked by these events also
become CL_COMPLETE, so marker event will also set to CL_COMPLETE. If there is no
user events, need wait last event complete and set marker event to complete.
Add barrier_index, for clEnqueueBarrier, point to user events, indicate the enqueue
apis follow clEnqueueBarrier should wait on how many user events.

Signed-off-by: Yang Rong <rong.r.yang@intel.com>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>