First part, updated most UTF8, hashing, memory and codecs. Except
utf8lower and upper, maybe a little later.
That includes huge amount of research with movemask dealing. Exact
details and blog post TBD.
When I tried to add cool new clang-tidy 14 warnings, I noticed that the
current clang-tidy settings already produce a ton of warnings. This
commit addresses many of these. Almost all of them were non-critical,
i.e. C vs. C++ style casts.
