stdbool not required
_vsnprintf and _snprintf are standard in MSVC since 2015, so I just use them directly now. They'll be replaced by std::fmt later anyways.
use <thread> for threading, instead of pthreads/windows.h thread directly
typedef -> using
include guards -> pragma once
typedef struct x { } y; -> struct y { }
some fixes to extremely old code that shouldn't be required any more