Fixed random crash on finalization of a Rados object by changing the signature
of rados_create to use PointerByReference instead of Pointer and then
storing the dereferenced clusterPtr in the Rados object.

For some reason the java finalizer sometimes first finalized the Memory
object and then the Rados object which lead to a crash when
dereferencing the clusterPtr in finalize().
Merge pull request #5 from kiefermat/clusterptr_finalize_crash

Fixed random crash on finalization of a Rados object