Fix MusicXML diminuendo <wedge> spread handling

[paxbun]

The MusicXML standard specifies that the spread attribute at the start of a crescendo and the end of a diminuendo is ignored. However, the current code only reads spread at the end of a <wedge> pair, which means it handles the spread of diminuendos wrongly.

This fix changes the behavior of MusicXmlInput so it sets the opening of a hairpin at the end for diminuendos or the start for crescendos. The followings show the result of this fix. Test MusicXML files are made by modifying <wedge> elements in BeetAnGeSample.musicxml from the example set on musicxml.com.

• test-narrow-wedge.musicxml (Made by replacing spread="15" with spread="5")

Before fix	After fix

• test-spread-0-at-dim-stop.musicxml (Made by adding spread="0" to the end <wedge> of diminuendos)

Before fix	After fix

[paxbun]

BTW, I've also just found that niente must be handled similarly (ignored at the end of a crescendo and the start of a diminuendo, which is the opposite of spread), but I've never seen this kind of notation, and I don't have any MusicXML file containing this. I don't know if making a similar change for this is okay.