Add basic collections.namedtuple implementation.
Add mp_obj_is_subclass_fast() - intended for fast argument checking.

I.e. as replacement of MP_OBJ_IS_TYPE(), which takes into account subclassing.
namedtuple: Inherit unary/binary ops from tuple base class.
Merge pull request #332 from pfalcon/namedtuple

Implement collections.namedtuple