If one calls `fundrawtransaction`, the change address will be retrieved from the keypool, though, this key/address will always be returned to the pool, leading to the problem that the next `getnewaddress()` call will restult in the same key/address.

Either we remove the auto-change-address (users would need to call `getrawchangeaddress` first [current best practice anyway]) or we add a call to keep/mark a specific key/address as change (after one have sent the funded raw transaction).

Reported by @NicolasDorier on IRC.
{
protected:
    CWallet* pwallet;
    int64_t nIndex;
    CPubKey vchPubKey;
public:
    CReserveKey(CWallet* pwalletIn)
    {
        nIndex = -1;
        pwallet = pwalletIn;
    }
    ~CReserveKey()
    {
        ReturnKey();
    }
    void ReturnKey();
    bool GetReservedKey(CPubKey &pubkey);
    void KeepKey();
    void KeepScript() { KeepKey(); }
};
/** 
 * Account information.
 * Stored in wallet with key "acc"+string account name.
 */
class CAccount