7.0 release notes should call out incompatible changes more clearly

I am aware of at least three non-backward-compatible changes in 7.0,
ie, things that will break existing applications in perhaps non-obvious
ways. I think the "Release Notes" document ought to call these out in a
separate section, rather than expecting people to examine the detailed
change list and intuit what those brief entries mean to them.

The three I can think of are:

1. If a GROUP BY item matches both an input column name and a
select-list label ("AS" name), 7.0 assumes the input column is meant.
This is compliant with the SQL92 spec. Unfortunately older versions
made the opposite choice.

2. SELECT DISTINCT ON syntax has changed --- now need parentheses
around the item being DISTINCT'ed.

3. User-defined operator names can't end in "+" or "-" unless they
also contain ~ ! @ # % ^ & | ` ? $ or :

Any others?

regards, tom lane