Sort out license problems

IANAL, but I think I am allowed to add missing copyright notices for
someone else. And I did my best job using git history to figure out who
wrote which functions. So I hope everything is fine.

CONTRIBUTORS

@@ -0,0 +1,38 @@
+Sorted in alphabeticall order
+
+Adam Jackson <ajax@nwnk.net>
+Brottweiler <tibell.christoffer@gmail.com>
+Carl Worth <cworth@cworth.org>
+Christopher Jeffrey <chjjeffrey@gmail.com>
+Corax26 <cor.ax26@gmail.com>
+Dana Jansens <danakj@orodu.net>
+Dave Airlie <airlied@linux.ie>
+dolio
+Duncan <duncan.britton@outlook.com>
+Einar Lielmanis <einars@gmail.com>
+Eric Anholt <anholt@freebsd.org>
+hasufell <julian.ospald@googlemail.com>
+James Cloos <cloos@jhcloos.com>
+Jamey Sharp <jamey@minilop.net>
+Jarrad <jarrad.whitaker@gmail.com>
+Javeed Shaikh <syscrash2k@gmail.com>
+Keith Packard <keithp@keithp.com>
+Kevin Kelley <kelleyk@kelleyk.net>
+mæp <m.aep@live.com>
+Mark Tiefenbruck <mark@fluxbox.org>
+Matthew Allum <breakfast@10.am>
+Michael Reed <supertron421@gmail.com>
+Nate Hart <nejsan@users.noreply.github.com> <nejthan@gmail.com>
+notfoss <static.vortex@gmx.com>
+Peter Mattern <matternp@arcor.de>
+Phil Blundell <pb@reciva.com>
+Que Quotion <quequotion@bugmenot.com>
+quequotion <the_q123@hotmail.com>
+Richard Grenville <pyxlcy@gmail.com>
+Scott Leggett <scott@sl.id.au>
+The Gitter Badger <badger@gitter.im>
+Tilman Sauerbeck <tilman@code-monkey.de>
+Tim van Dalen <Tim@timvdalen.nl>
+Uli Schlachter <psychon@znc.in>
+XeCycle <XeCycle@Gmail.com>
+Yuxuan Shui <yshuiv7@gmail.com>