feat: discover base classes in createstubs.py

[Josverl]

for a class Registry it is possible to discover the base classes from the __bases__ attribute

print ( [ b.__name__ for b in Registry.__bases__]) 
# or 
print ( ",".join([ b.__name__ for b in vfs.VfsPosix.__bases__ if b.__name__ != 'object']))

can be used to construct the classdef including the base classes