Include default hash functions for integers, add lookup function.
Include default hash functions for integers, add lookup function.

niklasso/minisat,meteor/minisat,meteor/minisat,robertsami/minisat,jamesbornholt/minisat,mabdula/minisat,meteor/minisat,mabdula/minisat,robertsami/minisat,jamesbornholt/minisat,niklasso/minisat,mabdula/minisat,meteor/minisat