Fix gcguard_delete for rb_objspace_call_finalizer
Fix gcguard_delete for rb_objspace_call_finalizer

rb_objspace_call_finalizer calls dfree functions in the order in which
the objects are lined up on the heap.  So the gcguard object may be
freed before the objects guarded in it.  This change avoids the
TypeError occurred on TypedData_Get_Struct in such the case.

mrkn/pycall.rb,mrkn/pycall,mrkn/pycall,mrkn/pycall.rb,mrkn/pycall.rb,mrkn/pycall,mrkn/pycall,mrkn/pycall.rb