[webrtc-pc] new commits pushed by alvestrand

The following commits were just pushed by alvestrand to https://github.com/w3c/webrtc-pc:

* Need <section> around dictionaries under RTCRtpSender

Fix for Issue https://github.com/w3c/webrtc-pc/issues/1749
  by aboba
https://github.com/w3c/webrtc-pc/commit/7d1559423483c963bdb276f9dcc71f16c98726d5

* Need <section> around RTCIceTransport dictionaries

Fix for Issue https://github.com/w3c/webrtc-pc/issues/1751
  by aboba
https://github.com/w3c/webrtc-pc/commit/71c56d68e75d5accec05bb1c5cf80c487eb7e91b

* Remove unnecessary dfn
  by Bernard Aboba
https://github.com/w3c/webrtc-pc/commit/7b810a49d63faef5dd9c8262ac505a54e119168e

* Merge pull request #1750 from aboba/master

Need <section> around dictionaries under RTCRtpSender and RTCIceTransport
  by Harald Alvestrand
https://github.com/w3c/webrtc-pc/commit/d682ab278ad104154b9f02af14b934cd3c76fc37