cppunit removal

AUTHOR: Ams Jeffries <squid3@treenet.co.nz>

The squid 3.0 will not be packaged with cppunit 1.10.0.

The developers have decided that the packaging of cppunit within the
squid sources has caused more trouble than was solved. Ease of install
independently of squid combined with the apparently widespread use of
cppunit as a standard tool we feel there is no need for it to be included.

For the initial release to date there will be no replacement testing
package and no automatic install for cppunit unless one is added by OS
distribution maintainers.

Squid releases already makes an attempt to detect external installs of
cppunit and use those by preference over the packaged version. This
existing detection has been left in place and will enable testing on any
system with cppunit. Maintainers and source testers will need to have
cppunit installed on their systems or not use "make check".