Problem:    xchacha20v2 crypt header is platform dependent.
Solution:   Avoid using "size_t". (Ozaki Kiichi, closses #12296)

Problem:    Decrypting with libsodium may fail if the library changes.
Solution:   Add parameters used to the encrypted file header. (Christian
            Brabandt, closes #12279)

Problem:    Crypt test is skipped if xxd is not found.
Solution:   Find xxd where it was supposed to be build.

Problem:    Typos in tests; one lua line not covered by test.
Solution:   Fix typos. Add test case. (Dominique Pellé, closes #9994)

Problem:    Crypt test fails on MS-Windows if xxd was not installed yet.
Solution:   Use the just built xxd executable if it exists. (James McCoy,
            closes #8929)

Problem:    When using xchaha20 crypt undo file is not removed.
Solution:   Reset 'undofile' and delete the file. (Christian Brabandt,
            closes #8630, closes #8467)

Problem:    Crypt test may fail on MS-Windows.
Solution:   Ignore "[unix]" in the file message. (Christian Brabandt,
            closes #8561)

Problem:    Crypt with sodium test fails on MS-Windows.
Solution:   Make the tests pass. (closes #8428)

Problem:    Available encryption methods are not strong enough.
Solution:   Add initial support for xchaha20. (Christian Brabandt,
            closes #8394)

Problem:    Various inconsistencies in test files.
Solution:   Add modelines where they were missing.  Use Check commands instead
            of silently skipping over tests.  Adjust indents and comments.
            (Ken Takata, closes #6695)