xml2guido: Fix for default-x note head positioning on different voices when different staves are present
xml2guido: Fix for default-x note head positioning on different voices when different staves are present

grame-cncm/libmusicxml,grame-cncm/libmusicxml,grame-cncm/libmusicxml,arshiacont/libmusicxml,dfober/libmusicxml,arshiacont/libmusicxml,arshiacont/libmusicxml,arshiacont/libmusicxml,arshiacont/libmusicxml,dfober/libmusicxml,grame-cncm/libmusicxml,grame-cncm/libmusicxml,dfober/libmusicxml,grame-cncm/libmusicxml,dfober/libmusicxml