bug#36583: 26.1; emacs 26 tries loading original user's .emacs after su to root

[Stefan Monnier]

> FWIW What broke things for me, was that it reads the .emacs file from
> /home/sb directory, but it doesn't read /home/sb/.emacs.d/elpa/ and
> therefore doesn't find the packages my .emacs refers to, so that startup
> breaks in the middle of the setup and nothing works as expected.

Indeed, as a first-approximation, it uses "~$LOGNAME/.emacs" but 
"$HOME/.emacs.d/elpa/".

In many circumstances "~$LOGNAME/" is the same as "$HOME/", and in yet
other circumstances Emacs uses "$HOME/.emacs" (which I find very handy)
rather than "~$LOGNAME/.emacs".

I'd rather we drop this special case of using "~$LOGNAME/.emacs" when we
decide that we're in "su".  I know it's long standing behavior, but
there are many other ways for the user to get the same result, so
I think we can get rid of this dangerous quirk.


        Stefan