Adding support for staff changes, phase 6
Adding support for staff changes, phase 6

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