history: fix encoding of history file

- Force to save file in UTF-8 encoding

Note: This does not produce a crash but the display
name is incorrectly rendered once reloaded from disk

Change-Id: I1a5cf22172a10c31d749170d20741966224392bc
Tuleap: #223

src/localhistorycollection.cpp

@@ -80,6 +80,7 @@ LocalHistoryCollection::~LocalHistoryCollection()
 
 void LocalHistoryEditor::saveCall(QTextStream& stream, const Call* call)
 {
+   stream.setCodec("UTF-8");
    const QString direction = (call->direction()==Call::Direction::INCOMING)?
       Call::HistoryStateName::INCOMING : Call::HistoryStateName::OUTGOING;