[MusicXML] Lineprall imports as downprall

1. Create new score.
2. Enable 'Note Entry'.
3. Enter note.
4. Disable 'Note Entry'.
5. Drag 'Lineprall' onto note from palette.
6. 'Export'.
7. Choose 'MusicXML'.
8. 'Save'.
9. Open MusicXML.

Result: Downprall appears instead of lineprall.

Using MuseScore 2.0 Nightly Build (46aafeb) - Mac 10.7.5.