Switch to C++ and modernize code?

[vlolteanu]

I've played around a bit with the code just for the hell of it. I see multiple avenues for improvement if we switch to C++. However, with all the already-open PRs (and the potential for conflicts), I'm not sure if any of this will make it in, so I'm leaving it as a draft.

Anyway...

• Manual memory management can be done away with almost entirely.
• I see what looks like a home-brewed RB tree. And a list. And Boyer Moor. This stuff can be replaced with implementations from STL. (BM is replaced in this PR.)
• All of the hoop-jumping to resolve paths properly can be handled by std::filesystem
• The way error handling is done is extremely tedious. There is a lot of duplicate code with checks to the err variable on almost every line. Consolidating stuff into functions and introducing exceptions would make it a lot easier to read.
• How reads and writes are used (not reading the full amount == error) is fundamentally flawed (but works in practice). You're not guaranteed to read the full amount, and you may even get EAGAIN or EINTR. These cases are benign; you just have to read/write the remainder.

All in all, I'd say a lot of code could be trimmed by switching to C++. I know my proposal throws a wrench in what you've got going, so it's no problem if you don't accept it.