bug#73431: Add `setf` support for `stream.el` in ELPA

[Okamsn]

Okamsn wrote:
> Philip Kaludercic wrote:
>> This definition also appears unchanged?  Please try to keep the diff as
>> small as possible.
> 
> OK. I have broken it into several files, which I've attached. How does
> it look now?

Hello,

In my previous message, I broke down the changes I made into 5 small 
files. Did that improve the clarity for you? Are there other changes 
that you would like for me to make?

Thank you.