[ale] Add optional log compression support.

Change-Id: Iba12f78fbf4a1331820a2cc69daa2ac234fd47bc
Reviewed-on: http://review.couchbase.org/37748
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>