Re: Use of system lisp when running freshly built emacs "in place"

[Richard Stallman]

    will cause the freshly built emacs to load lisp files from 
    /usr/share/emacs .

This is normal, since all versions of Emacs run files from
/usr/share/emacs.  Since that directory isn't part of the
distribution, it makes sense that even an uninstalled Emacs should use
it.  Things would not be particularly better if this problem
had showed up only when you someday install a new Emacs.

I wonder about two things:

1. Why did you install in /usr/share/emacs a copy of mwheel.elc
given that mwheel.el* is part of Emacs?

2. Why did that copy of mwheel.elc not define mouse-wheel-mode?  Is it
that the function mouse-wheel-mode did not yet exist in that version
of mwheel.el?