Fix lupdate errors

I suspect lupdate isn't smart enough to figure out what tr() is suppose
to do, so just make it a static function in class.
The error was: tr() cannot be called without context

src/base/net/downloadhandler.cpp

@@ -34,7 +34,6 @@
 #include <QNetworkAccessManager>
 #include <QNetworkCookie>
 #include <QNetworkProxy>
-#include <QNetworkReply>
 #include <QNetworkRequest>
 #include <QTemporaryFile>
 #include <QUrl>
@@ -46,9 +45,6 @@
 
 namespace
 {
-    QString tr(const char *message);
-    QString errorCodeToString(QNetworkReply::NetworkError status);
-
     bool saveToFile(const QByteArray &replyData, QString &filePath)
     {
         QTemporaryFile tmpfile {Utils::Fs::tempPath() + "XXXXXX"};
@@ -203,14 +199,7 @@ void Net::DownloadHandler::handleRedirection(QUrl newUrl)
     }
 }
 
-namespace
-{
-    QString tr(const char *message)
-    {
-        return QCoreApplication::translate("DownloadHandler", message);
-    }
-
-    QString errorCodeToString(QNetworkReply::NetworkError status)
+QString Net::DownloadHandler::errorCodeToString(const QNetworkReply::NetworkError status)
 {
     switch (status) {
     case QNetworkReply::HostNotFoundError:
@@ -259,4 +248,3 @@ namespace
         return tr("Unknown error");
     }
 }
-}

src/base/net/downloadhandler.h

@@ -30,10 +30,11 @@
 #ifndef NET_DOWNLOADHANDLER_H
 #define NET_DOWNLOADHANDLER_H
 
+#include <QNetworkReply>
 #include <QObject>
+
 #include "downloadmanager.h"
 
-class QNetworkReply;
 class QUrl;
 
 namespace Net
@@ -68,6 +69,8 @@ namespace Net
         void assignNetworkReply(QNetworkReply *reply);
         void handleRedirection(QUrl newUrl);
 
+        static QString errorCodeToString(QNetworkReply::NetworkError status);
+
         QNetworkReply *m_reply;
         DownloadManager *m_manager;
         const DownloadRequest m_downloadRequest;