These were originally deleted by mistake (because they were not yet being
installed) and are actually necessary.
This should have been part of r260576 but I missed committing this
directory.
MFC after: 5 days
This is because the atf vendor branch now includes a verbatim copy of
the distfile sources. As a result, the list of files to-be-removed from
the contrib/ directory is now more aggressive (and different) and the
upgrade notes now only describe stuff that is specific to the atf import
and is not documented in the Subversion Primer.
Approved by: rpaulo (mentor)