MB-10205: handle datatypes in xdcr

This includes passing datatypes untouched over xmem when destination
supports them. And uncompressing compressed bodies for capi and old
destinations.

Change-Id: Ia4a3bac27ae64459053e405e01861c8e80fd2a4b
Reviewed-on: http://review.couchbase.org/37561
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>