Object and class inspection functions

These are some functions for class/object inspection:

Function	Purpose
`is_object`	Check if a value is a class or object.
`is_class`	Check if a value is a class.
`is_instance`	Check if a value is a (sub)class or an instance of a (sub)class

`is_object(value [, name, ...])`

Returns:

false if value is not an object or class, i.e. is not a table or does not have a field __class which is a table.
else with one argument: the name of (the class of) value, i.e value.__class.__name.
else with 2+ arguments: the name of (the class of) value if it equals one of the extra arguments, or else nil.