[m-rev.] diff: avoid co-traversals in unify_proc.m

[Zoltan Somogyi]

Just simplifying some algorithms.

Zoltan.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Log.up
Type: application/octet-stream
Size: 750 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20170622/0480d47f/attachment-0002.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: DIFF.up
Type: application/octet-stream
Size: 49111 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20170622/0480d47f/attachment-0003.obj>