Bug 835542 - Add an IntegralConstant helper to TypeTraits.h, and use it where the spec says we should be using it.  r=bjacob

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extra : rebase_source : a1272a85489771ce1cbe5c3aaa678b5b04b49226
Bug 835542 - Implement mozilla::Abs.  r=Ms2ger

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extra : rebase_source : a3e62ff76365d27cc4cb10e4fee942ddb8b10b79