class library: fix curvelin

fixes #902

Signed-off-by: Tim Blechmann <tim@klingt.org>
class library: UGen - avoid numeric instability in lincurve/curvelin

Signed-off-by: Tim Blechmann <tim@klingt.org>
class library: ugen - use Select.multiNew

Signed-off-by: Tim Blechmann <tim@klingt.org>