- fix skip auth if `userauthlist` is NULL.
Closes#836 (Reported-by: @sudipm-mukherjee on github)
- fix most silenced `checksrc` warnings.
- sync examples/tests code between each other.
(output messages, error handling, declaration order, comments)
- stop including unnecessary headers.
- always deinitialize in case of error.
- drop some redundant variables.
- add error handling where missing.
- show more error codes.
- switch `perror()` to `fprintf()`.
- fix some `printf()`s to be `fprintf()`.
- formatting.
Closes#960