COSS removal from 3.0

COSS removal from 3.0

We had a vote on this some (several) months before 3.0 got branched, and
it was decided to drop COSS from the Squid-3.0 branch once branched.
Then the branching got delayed, and this task was forgotten when it
finally branched.

Until COSS gets significantly updated it's counter-productive to ship it
in STABLE releases. But the current code needs to be kept in trunk as
reference on how things got refactored for the day the current COSS code
gets forward ported to Squid-3.

Regards
Henrik