Bug 1041186, Part 1: Improve buffer overflow protection in mozilla::pkix, r=keeler

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extra : rebase_source : 0f4a33f2c66594930ba9c79233648c70e33ba27c
Bug 1041186, Part 2: Rename Input to Reader and InputBuffer to Input, r=keeler

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extra : rebase_source : bf57a9eb6ae5c122912e00a47156010e5ea99478