Studio:Sending and receiving broadcast messages in the Runtime

If broadcast messages are being sent from the target to the host (i.e., there are no subscribers on the target), the data must be marshalled up to the host. However, when both the broadcaster (owner) and a receiver (user) are on the target, it is more efficient to specify srST_RSP_PTR since only a pointer to the message is moved internally.

By contrast, if srST_RSP_VAL is specified, the entire message is copied before being sent.