Fixed reference counting bug in Python bindings when adding and removing signal callbacks.
Fixed reference counting bug in Python bindings when adding and removing signal callbacks.

davidhernon/libmapper-admin2,johnty/libmapper,davidhernon/libmapper-admin2,radarsat1/libmapper,davidhernon/libmapper-admin2,libmapper/libmapper,radarsat1/libmapper,davidhernon/libmapper-admin2,davidhernon/libmapper,malloch/libmapper,johnty/libmapper,libmapper/libmapper,malloch/libmapper,malloch/libmapper,libmapper/libmapper,johnty/libmapper,radarsat1/libmapper,davidhernon/libmapper,johnty/libmapper,libmapper/libmapper,davidhernon/libmapper,libmapper/libmapper,radarsat1/libmapper,malloch/libmapper,radarsat1/libmapper,davidhernon/libmapper,johnty/libmapper,libmapper/libmapper,davidhernon/libmapper-admin2,malloch/libmapper,malloch/libmapper,davidhernon/libmapper