`CompareModifiedEntry`, as used in

https://github.com/bitcoin/bitcoin/blob/3c098a8aa0780009c11b66b1a5d488a928629ebf/src/miner.h#L97-L112

will trigger a compile-time error in many `const` operations of index #1 of `indexed_modified_transaction_set` because `CompareModifiedEntry::operator()` is not `const`.

Most likely related to:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=224129
void operator() (CTxMemPoolEntry &e) { e.UpdateFeeDelta(feeDelta); }
private:
    int64_t feeDelta;
};
struct update_lock_points
{
    explicit update_lock_points(const LockPoints& _lp) : lp(_lp) { }
    void operator() (CTxMemPoolEntry &e) { e.UpdateLockPoints(lp); }
private:
    const LockPoints& lp;
};
struct mempoolentry_txid
{
    typedef uint256 result_type;
    result_type operator() (const CTxMemPoolEntry &entry) const
    {
        return entry.GetTx().GetHash();
    }
    result_type operator() (const CTransactionRef& tx) const
    {
        return tx->GetHash();
    }
};
/** \class CompareTxMemPoolEntryByDescendantScore
 *
 *  Sort an entry by max(score/size of entry's tx, score/size with all descendants).
 */
class CompareTxMemPoolEntryByDescendantScore