Update BWV988 v20

Update to LilyPond v2.18.2
Bar19: last treble note c5->c4, add tie
Bar21: bass, add tie to last e on first beat
Bar27: treble, last note remove staccatto
Bar29: bass, fis->f on last tuplet
Bar30: bass, a->c on first tuplet
(Javier Ruiz-Alma)
Close #101