[HACKERS] Draft release notes for next week's back-branch releases

I've written $SUBJECT ... you can find them at

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=54dbd4dc78b045ffcc046b9a43681770c3992dd4

and in an hour or so they should be built in the devel docs at

https://www.postgresql.org/docs/devel/static/release-9-6-3.html

As usual, this one page contains entries for all back branches;
I'll split them up later.

Please review by Sunday.
        regards, tom lane