Update AUTHORS, add issues_closed_for_0.15.md, tweak the release checklist slightly.

AUTHORS

@@ -7,8 +7,13 @@ Christopher Head <chead@chead.ca>
 Chris Wolfe <chriswwolfe@gmail.com>
 C. Watford (christopher.watford@gmail.com)
 Darjan Krijan <darjan_krijan@gmx.de>
+David McCann <mccannd@uk.ibm.com>
+dota17 <chenguopingdota@163.com>
+Eric Haszlakiewicz <erh+git@nimenees.com>
 Eric Hawicz <erh+git@nimenees.com>
+Gianluigi Tiesi <sherpya@netfarm.it>
 grdowns <grdowns@microsoft.com>
+hofnarr <hofnarr@hofnarr.fi>
 Ivan Romanov <drizt@land.ru>
 Jaap Keuter <jaap.keuter@xs4all.nl>
 janczer <menshikov.ivn@gmail.com>
@@ -18,13 +23,19 @@ Jonathan Wiens <j.wiens@teles.com>
 Jose Bollo <jose.bollo@iot.bzh>
 Keith Holman <keith.holman@windriver.com>
 Liang, Gao <liang.gao@intel.com>
+Marc <34656315+MarcT512@users.noreply.github.com>
 max <mpano91@gmail.com>
+Micah Snyder <micasnyd@cisco.com>
 Michael Clark <michael@metaparadigm.com>
 myd7349 <myd7349@gmail.com>
+Pascal Cuoq <cuoq@trust-in-soft.com>
 Pierce Lopez <pierce.lopez@gmail.com>
 Po-Chuan Hsieh <sunpoet@sunpoet.net>
 Ramiro Polla <ramiro.polla@gmail.com>
 Rikard Falkeborn <rikard.falkeborn@gmail.com>
 Robert <roby_p97@yahoo.com>
 Rubasri Kalidas <rubasri.kalidas@intel.com>
+Simon McVittie <smcv@collabora.com>
+Tobias Stoeckmann <tobias@stoeckmann.org>
+Tudor Brindus <me@tbrindus.ca>
 Unmanned Player <36690541+unmanned-player@users.noreply.github.com>