libjingle: stop building files in talk/base as they are no longer used as of r6799

BUG=3379
R=thorcarpenter@google.com

Review URL: https://webrtc-codereview.appspot.com/16189004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6802 4adac7df-926f-26a2-2b94-8c16560cd09d