Change how class init is handled

[litlighilit]

The class macro, derived from the old pylib, still rewrite the init function in a class definition block to a proc starting with "new".

But in Python, there is actually a __new__ method of each class, which is responsible to return a new instance. Thus this issue introduces the new function in a class being supported, and when new is defined, leave init only to init on the new-ed instance, and returns nothing.