mu/mu4e release 1.2

1.2

After a bit over a year since version 1.0, here is version 1.2. This is
mostly a bugfix release, but there are also a number of new features.

mu

- Substantial (algorithmic) speed-up of message-threading; this also (or
  especially) affects mu4e, since threading is the default. See commit
  eb9bfbb1ca3c for all the details, and thanks to Nicolas Avrutin.

- The query-parser now generates better queries for wildcard searches, by
  using the Xapian machinery for that (when available) rather than
  tranforming into regexp queries.

- The perl backend is hardly used and will be removed; for now we just
  disable it in the build.

- Allow outputing messages in json format, closely following the sexp
  output. This adds an (optional) dependency on the Json-Glib library.

mu4e

- Bump the minimal required emacs version to 24.4. This was already de-facto
  true, now it is enforced.

- In mu4e-bookmarks, allow the `:query` element to take a function (or
  lambda) to dynamically generate the query string.

- There is a new message-view for mu4e, based on the Gnus' article-view.
  This bring a lot of (but not all) of the very rich Gnus article-mode
  feature-set to mu4e, such as S/MIME-support, syntax-highlighting,

  For now this is experimental ("tech preview"), but might replace the
  current message-view in a future release. Enable it with:
           (setq mu4e-view-use-gnus t)

  Thanks to Christophe Troestler for his work on fixing various encoding
  issues.

- Many bug fixes

guile

- Now requires guile 2.2.

Contributors for this release:

Ævar Arnfjörð Bjarmason, Albert Krewinkel, Alberto Luaces, Alex Bennée, Alex
Branham, Alex Murray, Cheong Yiu Fung, Chris Nixon, Christian Egli,
Christophe Troestler, Dirk-Jan C. Binnema, Eric Danan, Evan Klitzke, Ian
Kelling, ibizaman, James P. Ascher, John Whitbeck, Junyeong Jeong, Kevin
Foley, Marcelo Henrique Cerri, Nicolas Avrutin, Oleh Krehel, Peter W. V.
Tran-Jørgensen, Piotr Oleskiewicz, Sebastian Miele, Ulrich Ölmann