take care of buffer_scale_factor < 0 in jack_port_get_buffer()
take care of buffer_scale_factor < 0 in jack_port_get_buffer()

git-svn-id: 9d792367086e53bac42cb25f723fe47762daf29a@3887 0c269be4-1314-0410-8aa9-9f06e86f4224

drobilla/jack1,drobilla/jack1,ventosus/jack1,drobilla/jack1,ventosus/jack1,ventosus/jack1,drobilla/jack1,adiknoth/tschack,adiknoth/tschack,ventosus/jack1