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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.
{
    QNetworkRequest netRequest;
    netRequest.setAttribute(QNetworkRequest::User, BIP70_MESSAGE_PAYMENTREQUEST);
    netRequest.setUrl(url);
    netRequest.setRawHeader("User-Agent", CLIENT_NAME.c_str());
    netRequest.setRawHeader("Accept", BIP71_MIMETYPE_PAYMENTREQUEST);
    netManager->get(netRequest);
}
void PaymentServer::fetchPaymentACK(CWallet* wallet, SendCoinsRecipient recipient, QByteArray transaction)
{
    const payments::PaymentDetails& details = recipient.paymentRequest.getDetails();
    if (!details.has_payment_url())
        return;
    QNetworkRequest netRequest;
    netRequest.setAttribute(QNetworkRequest::User, BIP70_MESSAGE_PAYMENTACK);
    netRequest.setUrl(QString::fromStdString(details.payment_url()));
    netRequest.setHeader(QNetworkRequest::ContentTypeHeader, BIP71_MIMETYPE_PAYMENT);
    netRequest.setRawHeader("User-Agent", CLIENT_NAME.c_str());
    netRequest.setRawHeader("Accept", BIP71_MIMETYPE_PAYMENTACK);
    payments::Payment payment;
    payment.set_merchant_data(details.merchant_data());
    payment.add_transactions(transaction.data(), transaction.size());
    
    QString account = tr("Refund from %1").arg(recipient.authenticatedMerchant);
    std::string strAccount = account.toStdString();
    std::set<CTxDestination> refundAddresses = wallet->GetAccountAddresses(strAccount);
    if (!refundAddresses.empty()) {
        CScript s = GetScriptForDestination(*refundAddresses.begin());