Do a round of copy-editing on the 9.5 release notes.

Also fill in the previously empty "major enhancements" list.  YMMV as to
which items should make the cut, but it's past time we had something more
than a placeholder here.

(I meant to get this done before beta2 was wrapped, but got distracted by
PDF build problems.  Better late than never.)

Author: tglsfdc