Move SetCurrentThreadName to platform_thread.* in rtc_base_approved,
update all webrtc and libjingle code to use the same function and remove
extra implementations.

BUG=
R=andresp@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/55439004

Cr-Commit-Position: refs/heads/master@{#9205}
10 files changed