SANE_FRAME_IR

Hi,
We have had a question from a developer regarding support for IR from a 
scanner, namely the LS-5000 supported by the coolscan3 backend.
This device can supply IR but there are a few different ways in which 
this can be delivered to the frontend. The brief discussion is here: 
https://gitlab.com/sane-project/backends/-/merge_requests/937

As I said in that discussion, I believe the SANE_FRAME_IR option (or 
some variant) is the better one to explicitly support it from the SANE 
standard. I assume that this was a proposed extension at some point. 
However, this would mean we would need to ratify a new standard and ask 
frontend developers to support the new features, something that we might 
struggle to do ourselves what with the backlog we currently have.

There are mentioned some other options, such as delivering the IR frame 
as grey in the next frame, which is done currently by another backend, 
and has the advantage of being supported right now.

Views? Any appetite for an update to the SANE Standard? I'm sure there 
are a few things that people would like to add.

Cheers,
Ralph