PUBLISH arbitrary presence body with pjsua-lib

[johan.lantz@xxxxxxxxxxx (Johan Lantz)]

You have this already in pjsip_pres_status:

pj_xml_node    *tuple_node;    /**< Pointer to tuple XML node of
                          parsed PIDF body received from
                          remote agent. Only valid for
                          client subscription. If the
                          last received NOTIFY request
                          does not contain any PIDF body,
                          this valud will be set to NULL */