These tests involves testing allocation-free function calling, and in strict
stackless mode, it's not possible to make a function call with heap locked
(because function activation record aka frame is allocated on the heap).
If heap allocation for the Python-stack of a function fails then we may
as well allocate the Python-stack on the C stack. This will allow to
run more code without using the heap.
gc.enable/disable are now the same as CPython: they just control whether
automatic garbage collection is enabled or not. If disabled, you can
still allocate heap memory, and initiate a manual collection.
Paul Sokolovsky