[PATCH 0/4] Update mu and autoload mu4e.

[Alex Kost <alezost@gmail.com>]

Hello, does anyone use mu4e (emacs interface for 'mu')?  If you do, may
I ask how?  By adding "~/.guix-profile/share/emacs/site-lisp/mu4e" to
'load-path' manually and requiring mu4e?

Our Emacs doesn't look in sub-directories of "share/emacs/site-lisp"
(only in "guix.d" subdir), so mu4e is not found automatically...
I've just thought that it would probably be better to look at site-lisp
subdirs and not to use a special "guix.d" directory, but it's for a
separate thread.

Returning to mu4e, I see that (require 'mu4e) is recommended¹, but IMO
requiring features in your ".emacs" is a bad practice.  I recommend to
avoid it if possible, because requiring big packages can significantly
reduce start-up time of your Emacs.  Instead you can wrap your settings
with 'with-eval-after-load' and use 'autoload' function if you need to
"pick" some command from a package.  Alternatively there is
'use-package' package².

After this patchset, "M-x mu4e" will be available right away (do not
require mu4e, as it will not be needed).

[PATCH 1/4] gnu: mu: Use 'modify-phases'.
[PATCH 2/4] gnu: mu: Install emacs files in a proper place.
[PATCH 3/4] gnu: mu: Install emacs autoloads.
[PATCH 4/4] gnu: mu: Update to 0.9.16.

¹ http://www.djcbsoftware.nl/code/mu/mu4e/Minimal-configuration.html#Minimal-configuration
² https://github.com/jwiegley/use-package