[Toybox] [PATCH] sed s///: support POSIX I as synonym for i

[enh]

the only two other things i've noticed in issue 8 that we don't
already have are `rm -d` (which is in coreutils but not busybox) and
`tail -r` (which is in neither).

funnily enough, the rationale for `tail -r` is that it's more widely
supported than tac ... which as far as i can tell for the systems i
have available, is only true on the mac.

but this sed s/// I versus i seemed more worthwhile.

On Fri, Mar 27, 2020 at 5:03 PM enh <enh at google.com> wrote:
>
> POSIX chose I rather than i as the case-insensitive flag for s///,
> because apparently more seds support I than i. We're allegedly alone in
> only supporting i. (On the Mac, sed supports neither.)
>
> Strictly this isn't *currently* in POSIX, but it's been accepted for
> issue 8.
>
> Bug: https://austingroupbugs.net/view.php?id=779#c2050
> ---
>  tests/sed.test   | 2 ++
>  toys/posix/sed.c | 3 ++-
>  2 files changed, 4 insertions(+), 1 deletion(-)