Collect all methods redefined in self

Property definitions

nitc :: model_collect $ MClass :: collect_redef_mmethods
	# Collect all methods redefined in `self`
	fun collect_redef_mmethods(filter: nullable ModelFilter): Set[MMethod] do
		var res = new HashSet[MMethod]
		for mproperty in collect_redef_mproperties(filter) do
			if mproperty isa MMethod then res.add(mproperty)
		end
		return res
	end
src/model/model_collect.nit:792,2--799,4