Copy RTCAudioSource.h and RTCMediaSource.h with other public header files when building the WebRTC framework for iOS / Mac

NOTRY=True

Review-Url: https://codereview.webrtc.org/2313473002
Cr-Commit-Position: refs/heads/master@{#14117}
diff --git a/AUTHORS b/AUTHORS
index 6d1ee96..729f804 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -33,6 +33,7 @@
 Saul Kravitz <Saul.Kravitz@celera.com>
 Silviu Caragea <silviu.cpp@gmail.com>
 Steve Reid <sreid@sea-to-sky.net>
+Vladimir Beloborodov <VladimirTechMan@gmail.com>
 Vicken Simonian <vsimon@gmail.com>
 Victor Costan <costan@gmail.com>