Non-PAM DHX2 / DHCAST128 auth doesn't work on macOS

[rdmark]

An AFPERR_AUTHCONT error is thrown for the AFP_LOGIN_EXT command when attempting to authenticate with DHX2 or DHCAST128, compiled without PAM support, on a macOS host.

Using netatalk without PAM would be handy on macOS when netatalk is packaged with Homebrew, because brew is sandboxed by default and cannot write the PAM config file.

[EricFromCanada]

Doesn't traditional *nix-style auth rely on /etc/shadow, which macOS doesn't have? Fairly sure that non-PAM auth in that case would need to query Directory Services directly, with e.g. /usr/bin/dscl . auth username password.

[rdmark]

Discarding this. Our build system is choosing only PAM auth by default when building on macOS, and I think it's a fine abstraction to use on this OS.