Merge branch 'stable-2.7' into stable-2.8

This fixes the problem with the distcheck-release target failing needlessly.

* stable-2.7:
  Improve check for  "unreleased" versions in NEWS

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Klaus Aehlig <aehlig@google.com>