CCBC-178: short require 2byte alignment

Change-Id: I556b4a19d495c46cfbdb9d4f8b4ad17789d11dd0
Reviewed-on: http://review.couchbase.org/24597
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>