PyPy: Destroy base PyObject on dealloc

Change-Id: I4a032e0862a82cb52269669c959145de762a0770
Reviewed-on: http://review.couchbase.org/29640
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Volker Mische <volker.mische@gmail.com>