VCS[git]: Limit text size to be displayed.

in VCSBaseEditor  and BaseTextEditor::createNew to the size
used for limiting file size.

Reviewed-by: Robert Loehning <robert.loehning@nokia.com>
Task-number: QTCREATORBUG-1847

src/plugins/texteditor/basetexteditor.h

@@ -294,6 +294,8 @@ protected:
     bool canInsertFromMimeData(const QMimeData *source) const;
     void insertFromMimeData(const QMimeData *source);
 
+    static QString msgTextTooLarge(quint64 size);
+
 private:
     void maybeSelectLine();