bug#4446: remove ###autoload from ediff-hook.el

[Dan Nicolaescu]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

  > > The ###autoload in ediff-hook.el is not needed, this file is in the
  > > dumped image, so the autoload's only effect is to make loaddefs.el
  > > bigger and increase the size of the dumped image.
  > 
  > > The comment in the file says that the autoload is needed for XEmacs, but
  > > that's not a good reason to keep it in the Emacs CVS, it's a one line
  > > change to a file that almost never changes.
  > 
  > > OK to remove the autoload line?
  > 
  > Actually, it reminds me that I faced a similar situation recently.
  > I did remove the autoload cookie, but in retrospect I think it was the
  > wrong thing to do.  We should instead teach our build system to skip
  > preloaded files when creating the loaddefs.el file.

I got rid of most of the autoloads in the preloaded files a couple of
years ago, this must have fallen through the cracks.
Skipping register.el while creating loaddefs.el would be wrong, nothing
else would create the register bindings then.
And there's 3 autoloads more in composite.el, that's all the autoloads
in the unconditionally preloaded files.
Given that there's so few autoloads left, it does not seem like a good
idea to change the build system instead of just removing them.

More, for the specific case of ediff-hook.el, IMO the best thing to do
is got fold the emacs specific contents of that file into menu-bar.el
and get rid of it.  Almost all of the menu creation happens in menu-bar.el...