Register buffers with an execution context.
template< typename Executor, typename MutableBufferSequence, typename Allocator> buffer_registration< MutableBufferSequence, Allocator > register_buffers( const Executor & ex, const MutableBufferSequence & buffer_sequence, const Allocator & alloc, typename constraint< is_executor< Executor >::value||execution::is_executor< Executor >::value >::type = 0);