For superclasses which have a non-invariant position, keep their position in virtual table

Property definitions

nitc :: virtual_machine $ MClass :: positions_methods=
	# For superclasses which have a non-invariant position, keep their position in virtual table
	var positions_methods: HashMap[MClass, Int] = new HashMap[MClass, Int]
src/vm/virtual_machine.nit:425,2--426,71