cpplint: declare bankruptcy

We have not pushed updates to the public cpplint code from our internal
version in years.  No one seems interested in picking it up either.

Since an open source community has formed & forked & updated it, let's
delete our ancient version and just send people to that project now.

cppguide.html

@@ -2171,7 +2171,7 @@ tool. </p>
 how to run <code>cpplint.py</code> from their project
 tools. If the project you are contributing to does not,
 you can download
-<a href="https://raw.githubusercontent.com/google/styleguide/gh-pages/cpplint/cpplint.py">
+<a href="https://raw.githubusercontent.com/cpplint/cpplint/HEAD/cpplint.py">
 <code>cpplint.py</code></a> separately.</p>
 </div>