[m-rev.] diff: factor out common code in modules.m

[Zoltan Somogyi]

This prepares for a later change.

Zoltan.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Log.grab1
Type: application/octet-stream
Size: 50 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20160811/815e85c7/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: DIFF.grab1
Type: application/octet-stream
Size: 8445 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20160811/815e85c7/attachment-0001.obj>