Fix FTBFS with GCC6

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit c82b0c25d8)

src/mainwidget.cpp

@@ -158,8 +158,8 @@ void MainWidget::fileSave() {
     if(salva)
     {
       m_outputFilename=saveFilename;
-      ifstream in(m_tmpFilename);
-      ofstream out(m_outputFilename);
+      ifstream in(m_tmpFilename.local8Bit());
+      ofstream out(m_outputFilename.local8Bit());
       if(!in || !out)
       {
         emit signalChangeStatusbar(i18n(i18n("Error while saving file")));
@@ -179,8 +179,8 @@ void MainWidget::fileSave() {
   }
   else if (m_changed)
   {
-    ifstream in(m_tmpFilename);
-    ofstream out(m_outputFilename);
+    ifstream in(m_tmpFilename.local8Bit());
+    ofstream out(m_outputFilename.local8Bit());
     if(!in || !out)
     {
       emit signalChangeStatusbar(i18n("Error while saving file"));
@@ -244,8 +244,8 @@ void MainWidget::fileSaveAs() {
     if(salva)
     {
       m_outputFilename=saveFilename;
-      ifstream in(m_tmpFilename);
-      ofstream out(m_outputFilename);
+      ifstream in(m_tmpFilename.local8Bit());
+      ofstream out(m_outputFilename.local8Bit());
       if(!in || !out)
       {
         emit signalChangeStatusbar(i18n("Error while saving file"));