LICENSES: Add license text files, add missing notices, fix SPDX tags

SPDX tags don't replace license files. Some notices were missing and
some tags were not according to the SPDX specification, too.

Now reuse --lint from the REUSE tool (https://reuse.software/) passes.

Reported-by: Martin Hauke <mardnh@gmx.de>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/checksum.c b/checksum.c
index 72a7bba..eccbdee 100644
--- a/checksum.c
+++ b/checksum.c
@@ -1,5 +1,4 @@
-// SPDX-License-Identifier: AGPL-3.0-or-later
-// SPDX-License-Identifier: BSD-3-Clause
+// SPDX-License-Identifier: AGPL-3.0-or-later AND BSD-3-Clause
 
 /* PASST - Plug A Simple Socket Transport
  *  for qemu/UNIX domain socket mode