Visible for testing.
Applies the lifting procedure described in "On Lifted Cover Inequalities: A
New Lifting Procedure with Unusual Properties", Adam N. Letchford, Georgia
The algo is pretty simple, given a cover C for a given rhs. We compute
a rational weight p/q so that sum_C min(w_i, p/q) = rhs. Note that q is
pretty small (lower or equal to the size of C). The generated cut is then
of the form
sum X_i in C for which w_i <= p / q
+ sum gamma_i X_i for the other variable <= |C| - 1.
gamma_i being the smallest k such that w_i <= sum of the k + 1 largest
min(w_i, p/q) for i in C. In particular, it is zero if w_i <= p/q.
Note that this accept a general constraint that has been canonicalized to
sum coeff_i * X_i <= base_rhs. Each coeff_i >= 0 and each X_i >= 0.