Use UINT64_C to define BP_DELETED_FLAG

Change-Id: Id50e1f221e33263bc1367eddbda5cbfc28ebe475
Reviewed-on: http://review.couchbase.org/31595
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>