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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.
{
    QLocalSocket *clientConnection = uriServer->nextPendingConnection();
    while (clientConnection->bytesAvailable() < (int)sizeof(quint32))
        clientConnection->waitForReadyRead();
    connect(clientConnection, SIGNAL(disconnected()),
            clientConnection, SLOT(deleteLater()));
    QDataStream in(clientConnection);
    in.setVersion(QDataStream::Qt_4_0);
    if (clientConnection->bytesAvailable() < (int)sizeof(quint16)) {
        return;
    }
    QString msg;
    in >> msg;
    handleURIOrFile(msg);
}
bool PaymentServer::readPaymentRequestFromFile(const QString& filename, PaymentRequestPlus& request)
{
    QFile f(filename);
    if (!f.open(QIODevice::ReadOnly)) {
        qWarning() << QString("PaymentServer::%1: Failed to open %2").arg(__func__).arg(filename);
        return false;
    }
    
    if (!verifySize(f.size())) {
        return false;
    }
    QByteArray data = f.readAll();
    return request.parse(data);
}
bool PaymentServer::processPaymentRequest(const PaymentRequestPlus& request, SendCoinsRecipient& recipient)