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### Issue description
The datadir field on the debug window displays incorrectly if the profile folder name is accented.

### How to reproduce
1. Create a profile with accented profile folder name (àèìòùáéíóú)
2. Run bitcoin core with the default datadir
3. Go to the debug window and look at the datadir field

### Expected behaviour
The datadir folder path should display correctly.

### Actual behaviour
Accented characters display as a unknown character question mark.

### Screenshots
![Debug Window](https://cloud.githubusercontent.com/assets/11365204/20029647/41dee90e-a352-11e6-8784-e5a48798d62e.png)


### Confirmed affected versions
The bug has been tested on the following implementations:

- v0.13.1 from source cross-compiled for Windows x64 on a Ubuntu 14.04 enviroment
- 0.13.0 official Windows x64 binary

### Additional debug info
Copying and pasting the text into a program that is known to support accented characters (Such as Notepad++) still displays unknown character symbols.
{
    
    Q_EMIT message(tr("Payment acknowledged"), paymentACKMsg, CClientUIInterface::ICON_INFORMATION | CClientUIInterface::MODAL);
}
bool PaymentServer::verifyNetwork(const payments::PaymentDetails& requestDetails)
{
    bool fVerified = requestDetails.network() == Params().NetworkIDString();
    if (!fVerified) {
        qWarning() << QString("PaymentServer::%1: Payment request network \"%2\" doesn't match client network \"%3\".")
            .arg(__func__)
            .arg(QString::fromStdString(requestDetails.network()))
            .arg(QString::fromStdString(Params().NetworkIDString()));
    }
    return fVerified;
}
bool PaymentServer::verifyExpired(const payments::PaymentDetails& requestDetails)
{
    bool fVerified = (requestDetails.has_expires() && (int64_t)requestDetails.expires() < GetTime());
    if (fVerified) {
        const QString requestExpires = QString::fromStdString(DateTimeStrFormat("%Y-%m-%d %H:%M:%S", (int64_t)requestDetails.expires()));
        qWarning() << QString("PaymentServer::%1: Payment request expired \"%2\".")
            .arg(__func__)
            .arg(requestExpires);
    }
    return fVerified;
}
bool PaymentServer::verifySize(qint64 requestSize)