These will always be byte streams at heart, so let's try to keep them
with a proper type. Should make it clearer how they will be used.

We mostly use classical C strings, but the memory management around them
can get confusing and error prone. Let's use std::string for the cases
where we need to return a newly allocated string.

Avoid our own custom types in favour of what's already included with
C++.

Avoid having our own custom stuff and instead use the modern, standard
types, for familiarity.

Everything else uses LF line endings, so fix up the few stray ones.