Update various copyright years.

diffoscope/__init__.py

diffoscope/comparators/__init__.py

diffoscope/comparators/binwalk.py

diffoscope/comparators/cbfs.py

diffoscope/comparators/deb.py

diffoscope/comparators/decompile.py

diffoscope/comparators/device.py

diffoscope/comparators/elf.py

diffoscope/comparators/macho.py

diffoscope/comparators/missing_file.py

diffoscope/comparators/pdf.py

diffoscope/comparators/python.py

diffoscope/comparators/rpm.py

diffoscope/comparators/rpm_fallback.py

diffoscope/comparators/sphinx.py

diffoscope/comparators/symlink.py

diffoscope/comparators/utils/compare.py

diffoscope/comparators/utils/container.py

diffoscope/comparators/utils/libarchive.py

diffoscope/comparators/zip.py