[commit/branch+head] Mention GDB 6.8.92 pre-prelease in ChangeLog

[Joel Brobecker]

> Now that GDB 6.8.92 is out, I have added the following GDB ChangeLog
> entry in both the branch and head, to document the time of creation of this
> pre-prelease.

Actually, I need to enhance my scripts, since the commit was only made
on the branch (this is only a pre-release, hardly worth mentioning
on the HEAD).

-- 
Joel