https://travis-ci.org/github/MarcoFalke/btc_nightly/jobs/680655419#L412
bool reserve()
    {
        assert(!m_could_reserve);
        std::lock_guard<std::mutex> lock(m_wallet.mutexScanning);
        if (m_wallet.fScanningWallet) {
            return false;
        }
        m_wallet.m_scanning_start = GetTimeMillis();
        m_wallet.m_scanning_progress = 0;
        m_wallet.fScanningWallet = true;
        m_could_reserve = true;
        return true;
    }
    bool isReserved() const
    {
        return (m_could_reserve && m_wallet.fScanningWallet);
    }
    ~WalletRescanReserver()
    {
        std::lock_guard<std::mutex> lock(m_wallet.mutexScanning);
        if (m_could_reserve) {
            m_wallet.fScanningWallet = false;
        }
    }
};
int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig = false) EXCLUSIVE_LOCKS_REQUIRED(wallet->cs_wallet);
int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig = false);
#endif