tcp_wrappers: Use ANSI (c89) function definitions

[emaste]

Summary

Although this code is in contrib/ there is no active upstream.

[emaste]

prompted by passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C2x from the function pointer call in options.c

[brooks]

Skimmed the diff and it looks fine. It's hard to imaging an error that would compile, but not work.

[dim]

I'm all fine with this, but ain't it time to, well, drop tcp wrappers? I can't imagine anyone seriously using it these days... :)