Add internal crypt & replace gethostbyaddr_r with getnameinfo

[rogersm]

Two commits (sorry!) to be able to compile in any modern unix:

• Added internal crypt to remove dependency with OS crypt

  We can move to some more modern hash in the future, but for now I wanted to keep compatibility.

• Replace gethostbyaddr_r with getnameinfo so it can be ported to modern unices/macOS

  No additional comments.

[rogersm]

Will rework and re-submit in two PR.