Link cJSON with m

Change-Id: Iea8a0c8668eb89c758e9b9f9cb038416562c58b0
Reviewed-on: http://review.couchbase.org/29914
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>