Improve 9.5 release notes.

Improve 9.5 release notes.

1) Add sgml comments referencing commits. This is useful to search for
   missing items etc.

   The comments containing the commit notes are an excerpt from:
   git log --date=short \
       --pretty='format:%cd [%h] %<(8,trunc)%cN: %<(48,trunc)%s%n%n%w(,4,4)%b%n' \
       $(git merge-base origin/master upstream/REL9_4_STABLE)..origin/master
2) Improve a handful of existing notes
3) Add missing entries about a couple features.
4) Add a bunch of straight-forward FIXMEs