Make a new attribute assignment

Property definitions

nitc $ ASTBuilder :: make_attr_assign
	# Make a new attribute assignment
	fun make_attr_assign(recv: AExpr, attribute: MAttribute, value: AExpr): AAttrAssignExpr
	do
		return new AAttrAssignExpr.make(recv, attribute, value)
	end
src/astbuilder.nit:89,2--93,4