gnu: Add Texinfo 6.1.

* gnu/packages/texinfo.scm (texinfo-6.1): New variable.
* gnu/packages/emacs.scm (emacs): Add comment about 'info.info'.

gnu/packages/emacs.scm

@@ -89,7 +89,8 @@ (define-public emacs
                 "pwd"))))
          (add-after 'install 'remove-info.info
            (lambda* (#:key outputs #:allow-other-keys)
-             ;; Remove 'info.info', which is provided by Texinfo.
+             ;; Remove 'info.info', which is provided by Texinfo <= 6.0.
+             ;; TODO: Remove this phase when we switch to Texinfo 6.1.
              (let ((out (assoc-ref outputs "out")))
                (delete-file
                 (string-append out "/share/info/info.info.gz"))

gnu/packages/texinfo.scm

 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2015 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014, 2016 Eric Bavier <bavier@member.fsf.org>
 ;;; Copyright © 2015 Mark H Weaver <mhw@netris.org>
 ;;;
@@ -62,6 +62,18 @@ (define-public texinfo
 is on expressing the content semantically, avoiding physical markup commands.")
     (license gpl3+)))
 
+(define-public texinfo-6.1
+  (package
+    (inherit texinfo)
+    (version "6.1")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append "mirror://gnu/texinfo/texinfo-"
+                                  version ".tar.xz"))
+              (sha256
+               (base32
+                "1ll3d0l8izygdxqz96wfr2631kxahifwdknpgsx2090vw963js5c"))))))
+
 (define-public texinfo-5
   (package (inherit texinfo)
     (version "5.2")