Bug 897305 - Improve String.prototype.repeat() performance; r=tschneidereit

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extra : rebase_source : eae8a917b902a88f60f8a2da14b0a8aed29db582
Bug 898653 - Quell 'not enough parameters for macro' warnings in MSVC. r=djvj

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extra : rebase_source : 7e467027c24b795d6764894c12290a630663830e