Suggested by @MarcoFalke after #14627 and possibly #14420. We should warn if an unrecognised/incorrect section is present in bitcoin.conf. i.e `[testnet]` is present instead of `[test]`.
#ifndef WIN32
#ifdef __linux__
#ifdef _POSIX_C_SOURCE
#undef _POSIX_C_SOURCE
#endif
#define _POSIX_C_SOURCE 200112L
#endif 
#include <algorithm>
#include <fcntl.h>
#include <sched.h>
#include <sys/resource.h>
#include <sys/stat.h>
#else
#ifdef _MSC_VER
#pragma warning(disable:4786)
#pragma warning(disable:4804)
#pragma warning(disable:4805)
#pragma warning(disable:4717)
#endif
#ifdef _WIN32_WINNT
#undef _WIN32_WINNT
#endif
#define _WIN32_WINNT 0x0501
#ifdef _WIN32_IE
#undef _WIN32_IE
#endif
#define _WIN32_IE 0x0501
#define WIN32_LEAN_AND_MEAN 1
#ifndef NOMINMAX
#define NOMINMAX