Refcounting

One of the simplest ways to implement a garbage collector is to use a reference counting algorithm. It goes something like this:

• All objects keep track of a reference_count integer.
• When that object is referenced, its reference count is incremented.
• When an object is garbage collected, the reference count of any object it references is decremented.
• When any object's reference count reaches zero, the object is garbage collected.

Assignment

1. In snekobject.h: add a new integer field named refcount to snek_object_t.
2. In snekobject.c: complete the _new_snek_object function:
   1. Allocate a snek_object_t on the heap using calloc so its memory is zero-initialized.
   2. If the allocation fails, return NULL.
   3. Set the refcount to 1.
   4. Return the pointer to the new object.