Bug 888593 - Move MozVoicemail to WebIDL. r=Ms2ger

--HG--
rename : dom/voicemail/nsIDOMMozVoicemail.idl => dom/webidl/MozVoicemail.webidl
Bumping gaia.json for 2 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/a429645dcb68
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #11814 from etiennesegonzac/bug-906775-call-group-handler

Bug 906775 - ConferenceGroupHandler r=rik

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https://hg.mozilla.org/integration/gaia-central/rev/c88a8a353458
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 906775 - ConferenceGroupHandler
r=rik