Add a 'request_id' to TID requests and responses

Add a 'request_id' to TID requests and responses

This adds a random hex string ID to each TID request. This is
propagated as the request is forwarded, then included in the response.
The field is not required, and is mostly an aid for debugging.

Adds two methods (tid_req_get_request_id and tid_resp_get_request_id)
to the public library interface.