Updating NEWS for 2.26

[Joseph Myers]

On Mon, 3 Jul 2017, Joseph Myers wrote:

> The NEWS section for security-related changes in 2.26 seems very 
> incomplete, with only a single entry.  It clearly needs to be filled out.  
> If people know of other significant changes missing from the main NEWS 
> section for 2.26, they should add those as well.

Reminder: the security-related section is still almost empty.  This needs 
to be fixed before the release.

-- 
Joseph S. Myers
joseph@codesourcery.com