Enable HAVE_GETPEERNAME when building curl (#304)

Looks like this enables a few optimizations internally, such as reusing
connections! Let's be sure to enable this for our platforms, which
should all have this, so we can get those performance optimizations with
HTTP.

curl-sys/build.rs

@@ -187,6 +187,7 @@ fn main() {
         .file("curl/lib/warnless.c")
         .file("curl/lib/wildcard.c")
         .define("HAVE_GETADDRINFO", None)
+        .define("HAVE_GETPEERNAME", None)
         .warnings(false);
 
     if cfg!(feature = "http2") {