Add meson build

Finally managed to finish this after spending too many time on games.

To simplify things (a lot) this MR does not implement auto detection of authentication scheme, though this will also allow closing #163 (closed) since pam support will no longer silently disabled 😂

Note that I was not able to test most of the scheme other than pam and generic shadow password.

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Closes: #157 (closed), #163 (closed)