[Pyrex] Segfault when using [nogc]

[Claudio Freire]

There's a segfault-kind of bug in code generation for [nogc] classes, in 0.9.9.

Even when the type object is of non-gc kind, it foces the GC
deallocator, which ends up segfaulting, due to
Compiler/TypeSlots.py:600:
GCDependentSlot("tp_free", "0", "_PyObject_GC_Del", dynamic = 1)

It's fixed by replacing, in Compiler/TypeSlots.py, line 182:

if scope.has_pyobject_attrs:

with

if scope.has_pyobject_attrs and not scope.no_gc: