PackagingDrafts/Duplicate Files

Clarification is to make clear that we're talking about duplication between subpackages as well as merely inside of a single subpackage.

Change to both the Guidelines and Review Guidelines. Text is currently the same in each.

Duplicate Files
A Fedora package must not list a file more than once in the spec file's %files listings.

Discussion
See Talk:PackagingDrafts/Duplicate Files for discussion.