Returns a flag if a presolve must be done before solving.
short is_do_presolve(lprec *lp);
is_do_presolve returns TRUE or FALSE. Do presolve or not.
The is_do_presolve function returns a flag if a presolve must be done
before solving. Presolve looks at the model and tries to simplify it so that
solving times are shorter. For example a constraint on only one variable is
converted to a bound on this variable (and the constraint is deleted). Note
that the model dimensions can change because of this, so be careful with this.
Both rows and columns can be deleted by the presolve.