Update btypes_meta.py

>>> import subclasses
>>> 
>>> subclasses.main()
ABCMeta
    abc
    /home/satishg/bin/blenderinstalldir/blender-2.70-linux-glibc211-x86_64/2.70/python/lib/python3.3/abc.py

bpy_struct_meta_idprop
    builtins
    <module 'builtins' (built-in)> is a built-in class

RNAMeta
    bpy_types
    /home/satishg/bin/blenderinstalldir/blender-2.70-linux-glibc211-x86_64/2.70/scripts/modules/bpy_types.py

MyMeta
    mytypes
    /home/satishg/musesatishg/blender/testing/pipeline/test1/btypes_meta.blend/mytypes.py