Last-minute updates for release notes.

Tom Lane <tgl@sss.pgh.pa.us>

Commit: f34f0e4c58a31e5edd3aa8a23e171fbcf7e01ff2
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2018-05-07T17:13:27Z
Releases: 11.0
Last-minute updates for release notes.

The set of functions that need parallel-safety adjustments isn't the
same in 9.6 as 10, so I shouldn't have blindly back-patched that list.
Adjust as needed.  Also, provide examples of the commands to issue.

Files