Proposal: don't install CNI headers by default

[Andrew Pinski]

> 
> Hi,
> 
> A large part of the time taken by "make install" is spent installing CNI
> headers.  I propose that we don't install them by default, and create an
> "install-cni-headers" target instead.

Actually I would be using the CNI headers if I have time to use them.
And I like the headers anyways as they are useful and quick reference
to what the classes define, without looking into the source.

-- Pinski