set -I is not required by standard, and does not match bash

[Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>]

Hello,

In dash, set -I is a short-option alias to set -o ignoreeof.

However, bash does not have such alias, it has an undocumented
set -I which switches off "invisible variables"
(I don't know what that is).

Standards do not mention any -I option.

I propose, in the interests of keeping things less disparate,
to remove set -I support from dash: make "ignoreeof" to be
only an -o long option.