[Cython] Control Flow

[Vitja Makarov]

I've recently fixed some issues:

 - closure variables were not tracked
 - scoped expression variables were initialized to None

So, I should fix broken tests, here are some of them:

nogil (should be fixed)
purecdef (upstream)
cfunc_directive_in_pyclass (upstream)
bufaccess_noassignT444 (should be removed?)
bufaccess (should be fixed)
ass2longlong (should be fixed)
builtinfuncs (should be fixed)
extcmethcall (should be fixed)
extcoerce (fixed or removed?)
e_extweakref (should be fixed)

-- 
vitja.