[m-rev.] diff: move error handling and foreign code blocks to the end of io.m

[Zoltan Somogyi]

This should not need review.

Zoltan.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Log.order
Type: application/octet-stream
Size: 393 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20220314/8613110f/attachment-0002.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: DIFF.order
Type: application/octet-stream
Size: 39449 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20220314/8613110f/attachment-0003.obj>