gnu: Add emacs-ag.

* gnu/packages/emacs.scm (emacs-ag): New variable.

Signed-off-by: Alex Kost <alezost@gmail.com>

gnu: Add font-wqy-microhei.

* gnu/packages/fonts.scm (font-wqy-microhei): New variable.

gnu: Add mlmmj.

* gnu/packages/mail.scm (mlmmj): New variable.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

doc: Add '--manifest' example using 'specification->package+output'.

* doc/guix.texi (Invoking guix package): Add --manifest example using
'specification->package+output'.

gnu: guile-json: Update to 0.6.0.

* gnu/packages/guile.scm (guile-json): Update to 0.6.0.

gnu: Add ocaml-ocurl.

* gnu/pcakages/ocaml.scm (ocaml-ocurl): New variable.

gnu: Add ocaml-jsonm.

* gnu/packages/ocaml.scm (ocaml-jsonm): New variable.

gnu: Add ocaml-uutf.

* gna/packages/ocaml.scm (ocaml-uutf): New variable.

gnu: Add ocaml-uchar.

* gnu/packages/ocaml.scm (ocaml-uchar): New variable.

gnu: Add ocaml-ulex.

* gnu/packages/ocaml.scm (ocaml-ulex): New variable.

gnu: Add ocaml-xmlm.

* gnu/packages/ocaml.scm (ocaml-xmlm): New variable.

gnu: Add ocaml-bos.

* gnu/packages/ocaml.scm (ocaml-bos): New variable.

gnu: Add ocaml-fpath.

* gnu/packages/ocaml.scm (ocaml-fpath): New variable.

gnu: Add ocaml-logs.

* gnu/packages/ocaml.scm (ocaml-logs): New variable.

gnu: Add r-msnid.

* gnu/packages/bioinformatics.scm (r-msnid): New variable.

gnu: Add r-msnbase.

* gnu/packages/bioinformatics.scm (r-msnbase): New variable.

gnu: Add r-pcamethods.

* gnu/packages/bioinformatics.scm (r-pcamethods): New variable.

gnu: Add r-mzid.

* gnu/packages/bioinformatics.scm (r-mzid): New variable.

gnu: Add r-vsn.

* gnu/packages/bioinformatics.scm (r-vsn): New variable.

gnu: Add r-affy.

* gnu/packages/bioinformatics.scm (r-affy): New variable.