Fix BZ #18757 - fmemopen fails to set errno on failure

[Andreas Schwab]

Paul Pluzhnikov <ppluzhnikov@google.com> writes:

>         [BZ #18757]
>         * libio/iofopncook.c (_IO_fopencookie): Set errno on failure
>         * libio/test-fmemopen.c (do_bz18820): Extend the test to cover BZ #18757

Ok.

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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