[Cbc] SOS: compatibility with ClpPresolve and / or CglPreProcess

[ycollet at freesurf.fr]

Hello,

A new question related to SOS constraints:

- can I use the CglPreProcess and / or CglPresolve classes with a  
CbcModel in which I add CbcSOS objects ?

I ask this question because I am still stuck with a problem when the  
solver is launched (I can't debug yet my scilab interface because  
scilab catches the signal emit by cbc). I think that the problem comes  
from the ClpPresolve class. For me, it seems that ClpPresolve is not  
usable with SOS constraints.
One of the classes (ClpPresolve and CglPreProcess) transforms the  
constraint matrix and not the sos constraints ...

YC