Add IPv6 configuration parameters to iOS API

Adds |disableIPV6| and |disableIPV6OnWiFi| properties to
RTCConfiguration

Bug: None
Change-Id: Id59fb2002afadd7817f7caeaa62231bf90ecb274
Reviewed-on: https://webrtc-review.googlesource.com/c/109280
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25496}
diff --git a/AUTHORS b/AUTHORS
index 4d43519..590a4c0 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -58,6 +58,7 @@
 Stefan Gula <steweg@gmail.com>
 Steve Reid <sreid@sea-to-sky.net>
 Tarun Chawla <trnkumarchawla@gmail.com>
+Uladzislau Susha <landby@gmail.com>
 Vladimir Beloborodov <VladimirTechMan@gmail.com>
 Vicken Simonian <vsimon@gmail.com>
 Victor Costan <costan@gmail.com>