note to packagers: notification of library version upgrades

[Bill Nottingham]

If you're upgrading a library to a new version that may cause rebuilds
to be needed, either in Core or Extras, *please* notify fedora-maintainers
so that other packagers can be aware of it.

These include things such as the recent flac or musicbrainz changes,
the upgrade from python-2.3 to python-2.4, or the openssl changes.

Bill