Bug 724768 - Store the various properties of Error objects in reserved slots, and eagerly create the stack string for them.  r=bhackett for the TI bits, r=jimb otherwise

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extra : rebase_source : b1fc9b1f09c36a9f936aa518d53001f430808f95
Bug 724768 - Set every blank class prototype as a delegate immediately after birth, so that we can properly and correctly cache the shape for new instances of that class that use that prototype.  r=bhackett

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extra : rebase_source : 082af2663a31d84de764865038ee949786d831e6