NAMING: elaborate why we don't use *_t and underscore prefixes#23

https://en.cppreference.com/w/c/language/identifier https://www.gnu.org/software/libc/manual/html_node/Reserved-Names.html https://stackoverflow.com/questions/224397/why-do-people-use-double-underscore-so-much-in-c https://stackoverflow.com/questions/10687053/meaning-of-double-underscore-in-the-beginning https://stackoverflow.com/questions/62734225/how-to-get-gcc-clang-to-error-on-reserved-identifiers https://devblogs.microsoft.com/oldnewthing/20230109-00/?p=107685