Access the vertx instance from HttpClient objects

[wzy1935]

Refers to eclipse-vertx/vertx-http-proxy#92

Hi, I'm contributing the API in vertx-http-proxy and there's a method I need to access the vertx instance from the HttpClient object, but currently there's no way to do this.

It could if we export the HttpClientInternal interface, by moving it from io.vertx.core.internal.http.impl to io.vertx.core.internal.http, then I can call it like this:

// client is an instance of HttpClient
Vertx vertx = ((HttpClientInternal) client).vertx();

Should we perform this change? I can make a PR for it.

[vietj]

right, this has not been done yet, will do that very soon @wzy1935