Bug 840888 - Add some localization notes to Metro locale files [r=jimm]

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extra : rebase_source : 2a2d1f08a523833d38e343e6ef48b1febec3ff40
Bug 828465 - Enable Metro UI for Windows 64 builds [r=jimm]

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extra : rebase_source : 702a38ec3dd427efe7298371c726a06dec6ce81a