Update some copyright years.

diffoscope/comparators/android.py

diffoscope/comparators/fsimage.py

diffoscope/comparators/pdf.py

diffoscope/comparators/pgp.py

diffoscope/comparators/rdata.py

diffoscope/comparators/rpm.py

diffoscope/comparators/squashfs.py

diffoscope/comparators/utils/archive.py

diffoscope/comparators/utils/libarchive.py

diffoscope/comparators/zip.py

diffoscope/diff.py

diffoscope/environ.py

diffoscope/presenters/html/html.py

diffoscope/presenters/html/templates.py

tests/comparators/test_elf.py

tests/comparators/test_macho.py

tests/comparators/test_pdf.py

tests/comparators/test_rpm.py