Make @host publicly accessible such as @port is in HTTP::Server

[joaodiogocosta]

I would like to be able to access an http server's @host the same way I can access @PORT.
As of this moment, @host is a private variable of HTTP::Server and does not have accessor methods.

I would be happy to submit a PR if you find it suitable.

[bcardiff]

There is a draft for splitting http server and listeners in order to support binding to unix socket directly #2735. That could impact on the solution for this.

Note that the ip used to bind the server to is not the same as the ip of the server itself. 0.0.0.0 matching everything but not telling you the ip of the server.

[joaodiogocosta]

@bcardiff I'll follow on #2735 and see what happens then. Thanks