Please update NEWS when backporting bug fixes to stable branches.

[Carlos O'Donell]

When backporting bugs to stable branches please:

- Create a new point release entry in NEWS if the previous
  release manager has't. I just did this for 2.23.1.

- Update NEWS with the bug you just fixed. We don't file
  distinct bugs for the point release so you must still
  update those bugs by hand.

  e.g.
~~~
Version 2.23.1

Security related changes:

  [Add security related changes here]

The following bugs are resolved with this release:

  [19679] gcc-4.9.3 C++ exception handling broken due to unaligned stack
~~~

This way we'll keep the point releases updated and listing
the bugs that were fixed by backports.

Cheers,
Carlos.