Coin / include / boost.README

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Regarding boost/, the boost header files are included here because we
use Boost.Test for a Coin testsuite, and when following all the potential
dependencies of boost/test/*, a lot of other boost headers are pulled in.

No boost headers should be installed with Coin, and no reference to boost
should be found in the public Coin headers.  Boost is not yet used
internally in the Coin library binary, only the testsuite uses boost.
This might change though.

For those who wonder, the boost headers are all from boost 1.45.0.