Oh dear, forgot this file in the turnstile commit.  This header defines the turnstile API and includes several comments.
Oh dear, forgot this file in the turnstile commit.  This header defines
the turnstile API and includes several comments.

Reminded by:	peter

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase