Switch to the real MIT license

Due to a copy/paste error, the COPYING file and subsequently created files
with the same content referred to the "Historical Permission Notice and
Disclaimer - sell variant", not the proper MIT license.

For the code, use SPDX license identifiers instead, this way the copy-paste
errors should be less likely to happen.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
2 jobs for wip/mit-license in 1 minute and 5 seconds (queued for 1 second)
Status Name Job ID Coverage
  Containers
passed fedora@container_build #8110024

00:00:17

 
  Build
passed fedora:32@default-build #8110025

00:00:48