Starting with txindex option produces a bug continually printing "y".

```
sudo apt-add-repository ppa:bitcoin/bitcoin
sudo apt-get update
bitcoind -daemon -txindex=1 -server=1 &
root@btc:~# Bitcoin server starting
: You need to rebuild the database using -reindex to change -txindex.

Do you want to rebuild the block database now?
yes
y
y
y
y
y
```

#ifndef BITCOIN_UI_INTERFACE_H
#define BITCOIN_UI_INTERFACE_H
#include <stdint.h>
#include <string>
#include <boost/signals2/last_value.hpp>
#include <boost/signals2/signal.hpp>
class CBasicKeyStore;
class CWallet;
class uint256;
class CBlockIndex;
enum ChangeType
{
    CT_NEW,
    CT_UPDATED,
    CT_DELETED
};
class CClientUIInterface
{
public:
    
    enum MessageBoxFlags
    {
        ICON_INFORMATION    = 0,
        ICON_WARNING        = (1U << 0),
        ICON_ERROR          = (1U << 1),