Adjust copyright statements for 2021

- Update DOSBox Staging Team copyright span to year 2021 (DOSBox Team
  copyrights left untouched).
- Add DOSBox Staging Team copyright line to files we extensively
  modified throughout 2020 (we add our copyright lines when number of
  non-trivially modified lines gets close to 50%).
- Change "dosbox-staging team" to "DOSBox Staging Team", in line with
  updated branding.
- Change MAME license identifiers to SPDX license identifiers.
- Cleanup some excessive whitespace around copyright statements.
- Do few adjustments to include order.
- Add few missing copyright identifiers (GPL-2.0-or-later,
  LGPL-2.1-or-later, BSD-3-Clause) as appropriate for specific file.
- Move SPDX identifiers to the top in scripts for consistency with other
  source files.
- Remove old copy of GPL2 license in italian from old translations.

scripts/count-pvs-bugs.py

@@ -1,7 +1,8 @@
 #!/usr/bin/python3
 
-# Copyright (C) 2020 Kevin Croft <krcroft@gmail.com>
 # SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright (C) 2020-2021  Kevin R. Croft <krcroft@gmail.com>
 
 """
 Count the number of issues found in an PVS-Studio report.