mu4e: Place provide forms in their own sections

Use "_" as the title of that section so that it is less distracting
when sections are collapsed to get an overview of the library.

Using a separate section is useful because it reduces the risk of
accidentally into the middle of a library.

mu4e/mu4e.el

@@ -63,7 +63,7 @@ window, unless BACKGROUND (prefix-argument) is non-nil."
       (when (y-or-n-p (mu4e-format "Are you sure you want to quit?"))
         (mu4e~stop))
     (mu4e~stop)))
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+;;; _
 (provide 'mu4e)
 ;;; mu4e.el ends here