[m-rev.] for review: Reduce use of foreign-exported procs in io.m.

[Julien Fischer]

Hi Peter,

On Mon, 3 Oct 2016, Peter Wang wrote:

> library/io.m:
>    Use foreign-exported enum for `file_type', replacing many
>    foreign-exported procs.
>
>    Move construction/deconstruction of Mercury structures out of
>    `file_modification_time_2', `file_type_2', `check_file_accessibility_2',
>    `check_directory_accessibility_dotnet', etc., removing the need for many
>    foreign-exported procs.
>
>    Delete `file_type_implemented'. `file_type_2' will return an error
>    code if necessary.

That looks fine.

Julien.