NEWS for 6.7: mention coverity bug fixes

[msnyder@sonic.net]

> I guess if Coverity is proprietary software then the Free Software line
> may be
> that it gets no mention.

That would be biting the hand that feeds us, wouldn't it?

Coverity donated a valuable service to FSF.  We benefitted
directly, thru the fixing of numerous potential crasher and
security risk bugs.  They charge most people for that service,
but they donated it to us for free.  This is not substantially
different from a for-profit employer donating the time of their
employees (such as most of us), and I should think we would
like to encourage it.

There is precident for acknowledging the contributions of
institutions and corporations in the NEWS file:

    Configurations for embedded MIPS now include a simulator
    contributed by Cygnus Solutions.

    Sparc configurations may now include the ERC32 simulator
    contributed by the European Space Agency.

What's wrong with acknowledging what Coverity has contributed?