Adding username to RTCIceServer

Adding username to RTCIceServer
https://bugs.webkit.org/show_bug.cgi?id=120861

Patch by Thiago de Barros Lacerda <thiago.lacerda@openbossa.org> on 2013-09-09
Reviewed by Eric Carlson.

No new tests needed. Existing media stream tests already cover it

* Modules/mediastream/RTCPeerConnection.cpp:
(WebCore::RTCPeerConnection::parseConfiguration):
* platform/mediastream/RTCConfiguration.h:
(WebCore::RTCIceServer::create):
(WebCore::RTCIceServer::username):
(WebCore::RTCIceServer::RTCIceServer):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@155346 268f45cc-cd09-0410-ab3c-d52691b4dbfc