Built against `master` branch 801dd40666d1e6009920ad3ff755c7bb993b2a62:

If I have no wallet.dat file and run:

    bitcoind -usehd=0

A new wallet.dat file is created and an HD seed is assigned.

I see an error message in the source:

    "Error loading %s: You can't disable HD on an already existing HD wallet or create new non-HD wallets."

but that doesn't get shown because `fFirstRun` is true, and so the code which checks for `-usehd` values doesn't run.

If it's no longer possible to create non-HD wallets, specifying -usehd=0 when creating a wallet should be an error, and not get silently ignored.
int nVersion = s.GetVersion();
        if (!(s.GetType() & SER_GETHASH))
            READWRITE(nVersion);
        
        READWRITE(nCreditDebit);
        READWRITE(nTime);
        READWRITE(LIMITED_STRING(strOtherAccount, 65536));
        if (!ser_action.ForRead())
        {
            WriteOrderPos(nOrderPos, mapValue);
            if (!(mapValue.empty() && _ssExtra.empty()))
            {
                CDataStream ss(s.GetType(), s.GetVersion());
                ss.insert(ss.begin(), '\0');
                ss << mapValue;
                ss.insert(ss.end(), _ssExtra.begin(), _ssExtra.end());
                strComment.append(ss.str());
            }
        }
        READWRITE(LIMITED_STRING(strComment, 65536));
        size_t nSepPos = strComment.find("\0", 0, 1);
        if (ser_action.ForRead())
        {
            mapValue.clear();