Taken at commit 51bf06502c46ee6c1f587459e8370aef11a3422d from the
tor-browser-24.2.0esr-1 branch from https://git.torproject.org/tor-browser.git.

On the long run, we want to do this at build time, just like the TorBrowser.
However, fiddling with the build options two days before a Tails release seems
crazy, so let's disable this with a pref for now.

Successfully tested on http://mozilla.github.io/webrtc-landing/ and
http://net.ipcalf.com/.

Document that -l10n must be told about the release schedule as well, and write email addresses in full.