Merge changes from topic 'okhttp2-upgrade'

* changes:
  Apply upstream commit: Let SocksProxy use the same definition of localhost as MockWebServer.
  Apply upstream commit: Reduce memory requirements for MockWebServerTest.disconnectHalfway().
  Reapply: Relax validation of HTTP header values to retain L/M behavior
  Reapply an upstream OkHttp change to Android for HttpUrl
  Apply upstream commit: Add basic URLFilter for HttpURLConnection
  Workaround for request header values with trailing '\r' or '\n'
  Android modifications to existing files from OkHttp / okio
  Android additions to OkHttp
  Update OkHttp to 2.7.5 and advance okio by one commit.