Proposal for passing a structure to ACL checking routines

In order to efficiently create an _external ACL checking_ function, it would be really convenient to have access to the full request made by the remote user.
The structure I've created here allow access to
 * user (as before)
 * requested command
 * requested subcommand
 * requested arguments

This could allow further development of a very _generic_ external ACL checking function that has access to all those informations to allow or deny access.