Memory is allocated but isn't deallocated in MainWindow::load and MainWindow::save

```
I found calloc calls in these functions, but didn't corresponding free()
calls. It looks like we have a mem leakage here.
I assign this issue to Le Ha, as the problem seems to have been existing
since the first checkin of gui_mw.cpp (r167).
```

Original issue reported on code.google.com by `zolotukhinm` on 24 Apr 2010 at 8:46
