spdx: update to SPDX license list version: 3.11 2020-11-25 (canonical…

…#9629)

Some licenses were missing. Update to the latest version of the SPDX license
list.

Fixes: https://bugs.launchpad.net/snapcraft/+bug/1903609

* spdx: add deprecated license IDs

Some deprecated license IDs may be in common use, eg. GPL-2.0, GPL-3.0.

Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>

* spdx: drop implicit handling of 'or-later' licenses

Some licenses had 'or-later' variants, eg. GPL-2.0+. The code would incorrectly
treat such licenses and lics as 'gnuplot+' would validate correctly even though
it is unexpected.

Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>

* spdx: add a test case for GPL-2.0++ license

Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>

* spdx: update to 3.11 2020-11-25 version of license list data

Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>