RE: buffer name completion is case-sensitive now

[Drew Adams]

I said:

> I think we should add a user option for this, similar to
> `read-file-name-completion-ignore-case': 
> `buffer-name-completion-ignore-case'.

Implementation of respect for such an option would likely be limited to
`read-buffer' and `interactive' buffer specs ("B" and "b").

Unlike the case for `read-file-name' and
`read-file-name-completion-ignore-case', it is impossible for `completing-read'
to reliably determine whether its completion candidates are (all) buffer names.