Update accent feature extraction.
Update accent feature extraction.

craigsapp/minHumdrum,craigsapp/humlib,humdrum-tools/minHumdrum,craigsapp/humlib,craigsapp/minHumdrum,craigsapp/minHumdrum,humdrum-tools/minHumdrum,craigsapp/humlib,humdrum-tools/minHumdrum