[Lazarus] real user name

[Marco van de Voort]

In our previous episode, Andrea Mauri said:
> I solved using GetUserData procedure from users unit.
> 
>   GetUserData(FpGetuid, Data);
>   Result.Name:= Data.pw_name;
>   Result.Real_name:= Data.pw_gecos;
>   Result.User_id:= Data.pw_uid;
>   Result.Group_id:= Data.pw_gid;
>   Result.home_dir:= Data.pw_dir;
>   Result.shell:= Data.pw_shell;

Note that that avoids _unit_ libc but not _library_ libc.

That said, the above example code will probably work well on FreeBSD and OS
X too (contrary to _unit_ libc)