[m-rev.] for review: Make some I/O predicates exception-safe.

[Peter Wang]

On Thu, 29 Sep 2016 16:35:01 +1000, Peter Wang <novalazy at gmail.com> wrote:
> +* We have made these predicates exception safe: the current input or output
> +  stream is restored to the original stream if an exception is thrown during
> +  their exception:

Bah, execution