code: private void strengthen(final CLClause c, final int remove) {
          if (c.dumped() || satisfied(c)) { return; }
          assert this.addedlits.empty();
          for (int i = 0; i < c.lits().size(); i++) {
              final int lit = c.lits().get(i);
              if (lit != remove && val(lit) == 0) { this.addedlits.push(lit); }
          }
          newPushConnectClause();
          this.addedlits.clear();
          dumpClause(c);
      }
docs: Removes a literal in a clause.
  @param c      the clause
  @param remove the literal to remove