code: void addQuaternaryClause(final MiniSatStyleSolver s, int a, int b, int c, int d) {
      this.addQuaternaryClause(s, a, b, c, d, LIT_UNDEF);
    }
docs: Adds a quaterary clause to the given SAT solver.
  @param s the sat solver
  @param a the first literal
  @param b the second literal
  @param c the third literal
  @param d the fourth literal