Adds PRESUBMIT.py dispensation for depending on rtc_base.

Dispensation for: a few test suites, desktop capture and libjingle.

BUG=N/A
R=kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/31549004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7356 4adac7df-926f-26a2-2b94-8c16560cd09d