mdbx: big-bang (initial).

- OS Abstraction Layer;
 - Windows Support.
 - preparation for more changes.

Change-Id: I53772eda9091ba361cbc9a28656190ea0d4c5cee

AUTHORS

@@ -0,0 +1,27 @@
+Contributors
+============
+
+Alexey Naumov <alexey.naumov@gmail.com>
+Chris Mikkelson <cmikk@qwest.net>
+Claude Brisson <claude.brisson@gmail.com>
+David Barbour <dmbarbour@gmail.com>
+David Wilson <dw@botanicus.net>
+Hallvard Furuseth <hallvard@openldap.org>, <h.b.furuseth@usit.uio.no>
+Heiko Becker <heirecka@exherbo.org>
+Howard Chu <hyc@openldap.org>, <hyc@symas.com>
+Ignacio Casal Quinteiro <ignacio.casal@nice-software.com>
+Jean-Christophe DUBOIS <jcd@tribudubois.net>
+John Hewson <john@jahewson.com>
+Kurt Zeilenga <kurt.zeilenga@isode.com>
+Leonid Yuriev <leo@yuriev.ru>, <lyuryev@ptsecurity.com>
+Lorenz Bauer <lmb@cloudflare.com>
+Luke Yeager <lyeager@nvidia.com>
+Martin Hedenfalk <martin@bzero.se>
+Ondrej Kuznik <ondrej.kuznik@acision.com>
+Orivej Desh <orivej@gmx.fr>
+Oskari Timperi <oskari.timperi@iki.fi>
+Pavel Medvedev <pmedvedev@gmail.com>
+Philipp Storz <philipp.storz@bareos.com>
+Quanah Gibson-Mount <quanah@openldap.org>
+Salvador Ortiz <sog@msg.com.mx>
+Sebastien Launay <sebastien@slaunay.fr>