Use qUtf8Printable() for logging strings

qDebug(), qInfo(), qWarning(), qCritical(), qFatal() expect %s arguments
to be UTF-8 encoded, while qPrintable() converts to local 8-bit encoding.
Therefore qUtf8Printable() should be used for logging strings instead of
qPrintable().

src/base/net/proxyconfigurationmanager.cpp

@@ -153,7 +153,7 @@ void ProxyConfigurationManager::configureProxy()
         }
 
         qDebug("HTTP communications proxy string: %s"
-               , qPrintable((m_config.type == ProxyType::SOCKS5) || (m_config.type == ProxyType::SOCKS5_PW)
+               , qUtf8Printable((m_config.type == ProxyType::SOCKS5) || (m_config.type == ProxyType::SOCKS5_PW)
                             ? proxyStrSOCK : proxyStrHTTP));
     }