review webrtc

see this proposal that me and the arkenfox maintainer worked on, in particular this comment.

basically:

• we wouldn't disable webrtc anymore, but we would still protect the private IP (thanks to mDNS) unless the user reverted a pref AND allowed camera or mic access during the call.
  • calls as spectator should work without any tweak and any leak, at least on some websites.
  • with the current prefs users need to revert two prefs, and if they want to use camera or mic the private IP is still needed, so end result is the same.
  • usually camera and mic access are allowed only on trusted websites, so it's not a big issue.
• when using a VPN the IP is still partially protected in every case.

note: win7 and win8.x do not support mDNS natively, but other prefs still cover potential leakage.

it would be one change in the .cfg and then an update of the FAQ (media.peerconnection.ice.no_host could still cause breakage on some website / when sharing audio or video).

edit: media.peerconnection.ice.no_host could also be removed if we don't think win7 and win8 are relevant anymore, it would reduce breakage.