CUDD, Sylvan : Add BDD Variants

[SSoelvsten]

With #110 , the benchmarks differentiate between BDDs with and without complement edges. BDD packages that support Multi-terminal BDDs can fake disabling complement edges by working with Integer leaves 0 and 1. This would be interesting to include, to be able gauge the effectiveness of this optimization in each benchmark.

• [x] CUDD using its ADDs ( #142 )
• [ ] Sylvan using its MTBDDs

[nhusung]

I think this only is possible for CUDD. As I read it, Sylvan implements MTBDDs with complement edges:

https://github.com/trolando/sylvan/blob/77e8e6f02fdac0ab079c8d79f008812bafd1a3a7/src/sylvan_mtbdd_int.h#L40-L66

[SSoelvsten]

I asked Tom, and he confirmed one can do it with Integer leaves 0 and 1 rather than the Boolean false and true.