Send parametrised control commands to the engine. The possibilities to send
down an integer, a pointer to data or a function pointer are provided. Any of
the parameters may or may not be null, depending on the command number. In
actuality, this function only requires a structural (rather than functional)
reference to an engine, but many control commands may require the engine be
functional. The caller should be aware of trying commands that require an
operational ENGINE, and only use functional references in such situations.
Send parametrised control commands to the engine. The possibilities to send down an integer, a pointer to data or a function pointer are provided. Any of the parameters may or may not be null, depending on the command number. In actuality, this function only requires a structural (rather than functional) reference to an engine, but many control commands may require the engine be functional. The caller should be aware of trying commands that require an operational ENGINE, and only use functional references in such situations.