Add referenced files to CMakeLists.txt
Add referenced files to CMakeLists.txt

Not necessary for build support, but gives better project
output for visual studio/clion etc

Change-Id: Ib3271bfbed17c173c6ec32810f8b471b9c6a6a1d
Reviewed-on: http://review.couchbase.org/52910
Reviewed-by: Daniel Owen <b3fc0e1a51f252986e60be7da121b74d3ac6845f@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

daverigby/kv_engine,owendCB/memcached,couchbase/memcached,couchbase/memcached,daverigby/kv_engine,daverigby/memcached,daverigby/memcached,couchbase/memcached,cloudrain21/memcached-1,cloudrain21/memcached-1,cloudrain21/memcached-1,daverigby/memcached,owendCB/memcached,cloudrain21/memcached-1,daverigby/kv_engine,daverigby/memcached,owendCB/memcached,couchbase/memcached,daverigby/kv_engine,owendCB/memcached