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