Differentiate unsupported procs from unimplemented procs

[ike709]

Currently, all procs just use set opendream_unimplemented = 1 if they're not currently implemented.

However, some procs (particularly related to the hub like GetMedal()) likely won't ever be supported and should instead use a new set like set opendream_unsupported = "Reason" to differentiate them from unimplemented procs that we just haven't gotten around to yet.

This could be used by the OD DM reference and could also reduce compiler emission spam by being a different pragma.