Updated HttpServer documentation to specify that only IPv6 connections can be made when specifying …

sdk/lib/io/http.dart

Index: sdk/lib/io/http.dart
diff --git a/sdk/lib/io/http.dart b/sdk/lib/io/http.dart
index 9e4e6a6b24c8bd698f1f3408fab48c629e2a4bbd..3d76df35563206f43699b9732addad1a9d2b82e6 100644
--- a/sdk/lib/io/http.dart
+++ b/sdk/lib/io/http.dart
@@ -224,7 +224,9 @@ abstract class HttpServer implements Stream<HttpRequest> {
    * If an IP version 6 (IPv6) address is used, both IP version 6
    * (IPv6) and version 4 (IPv4) connections will be accepted. To
    * restrict this to version 6 (IPv6) only, use [v6Only] to set
-   * version 6 only.
+   * version 6 only. However, if the address is
+   * [InternetAddress.LOOPBACK_IP_V6], only IP version 6 (IPv6) connections
+   * will be accepted.
    *
    * If [port] has the value [:0:] an ephemeral port will be chosen by
    * the system. The actual port used can be retrieved using the