[Clp] Suppress outout in Clp

[Horand Gassmann]

I am working on the new release of the OS project and am testing a number of
solvers on all sorts of problems. Since OS is conceivably used over a network,
we want to minimize the output, so we are setting osiHintStrength to the lowest
output level possible. On one of the problems cbc gives the informative output

Presolve thinks problem is unbounded

Since we intercept the actual return code later, this message is not
particularly relevant and we would like to suppress it. We have not found a way
to so, however. Can it be done?

Cheers

gus gassmann