Add a C++ interface to the random generators

Change-Id: I30b9a943a7a1fd20495adb8ac735209e0c7444ee
Reviewed-on: http://review.couchbase.org/32590
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>