Unix socket support

[jo2wan]

Hi, I have a quick question,

It seems I have to add some options to build.rs to compile libcurl with unix socket support. Is it possible to pass those flags from a cargo.ml? I don't want to get the curl-sys locally with the two extra flags only.
Or maybe the way forward would be to create a specific feature.

[alexcrichton]

I believe this was added in #154, but feel free to comment here if that doesn't work!

[jo2wan]

it does not work, when you libcurl is not installed on the machine and when you compile it from build.rs.
I had to add the two following flags in the build.rs (which is not really convenient as I have to use a local version of curl-rust crate)

    cfg.define("USE_UNIX_SOCKETS", None)
        .define("HAVE_SYS_UN_H", None);

[alexcrichton]

Ah ok, good to know! Want to send a PR with that update?

[sagebind]

This has now been added and published in version 0.4.31!