[RFA] Remove target_fileio_close_cleanup

[Simon Marchi]

On 2018-03-14 01:38 PM, Tom Tromey wrote:
> This removes target_fileio_close_cleanup in favor of a new RAII class.
> The new class is similar to scoped_fd but calls
> target_fileio_close_cleanup rather than close.
> 
> Regression tested by the buildbot.

LGTM.

Simon