Commit 958dd3ce68 will break emacs interface after "guix pull"

[Alex Kost]

Note: if you use emacs interface from a git checkout [as described in
the bottom of (info "(guix) Emacs Initial Setup")], everything should
work as expected.

Hello Ludo, this is not related to system tests, but in this patchset
you also moved 'memoize' to (guix combinators).  In commit 86670ca4b7 I
adjusted emacs interface to use it.

However, it is not enough (see [1]): currently, if a user does "guix
pull", (s)he gets the recent guile code with the new (guix combinators)
module, but the emacs stuff is still old as it comes with the
development snapshot.

So in this case emacs interface will not work (complaining about unbound
'memoize' variable).  So I think it's the time to update guix-devel
package.  Is it OK to do it now?

In general, it is not perfect that "guix pull" updates only guile
modules, and not emacs interface.  I recall there were similar (but much
smaller) breakages when emacs stuff and guile code (from
"~/.config/guix/latest") were out of sync.

I'm just whining, I don't have a wish to improve "guix pull" :-)

[1] https://gnunet.org/bot/log/guix/2016-05-05#T1020612

-- 
Alex