smap: New function smap_add_nocopy().

An upcoming commit will add a caller that needs to format both the key and
the value.  That isn't cleanly possible with the current interface.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Gurucharan Shetty <gshetty@nicira.com>
ofproto: Report controller rate limiting statistics in database.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Gurucharan Shetty <gshetty@nicira.com>