guix: utils: Re-export 'memoize'.

Suggested by Ludovic Courtès <ludo@gnu.org>.

* guix/utils.scm: Re-export 'memoize' to avoid a potential breakage of
  emacs interface.  See
  <http://lists.gnu.org/archive/html/guix-devel/2016-05/msg00146.html>
  for details.

guix/utils.scm

@@ -44,6 +44,7 @@
   #:use-module (ice-9 format)
   #:use-module ((ice-9 iconv) #:select (bytevector->string))
   #:use-module (system foreign)
+  #:re-export (memoize)         ; for backwards compatibility
   #:export (bytevector->base16-string
             base16-string->bytevector