ceph_json: add template specializations

Missing template specializations for data types that
needed for 32 bit compilation

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
ceph_json: add missing include file

Needed for LONG_MAX and friends

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
Merge pull request #172 from ceph/wip-ceph-json

Wip ceph json

Reviewed-by: Sage Weil <sage@inktank.com>