- remove __attribute__(format) checker for UTF8 char type printf becuase it forcely require the type of format string is const char*, rather than const char8_t*, and I can not use any switches to remove this.
- delete useless macro and header in clap manual.
- add compiler hint for checking the arguments of printf.
- change the return value of printf. from std::expected to normal value. use C++ exception to indicate error.
* the error of printf usually caused by programmer. so it can be found when testing program.
* so i use std::logic_error to indicate this and programmer should fix this before releasing program.
- change the use of encoding convertion. for those cases that convertion must be safe, we unwrap it directly.
