int ctl_xively_feed_has_pending_data(CTL_XIVELY_FEED_t *self);
ctl_xively_feed_has_pending_data returns non-zero if any of the datastreams registered with the feed self have outstanding data that has not been pushed to Xively using ctl_xively_feed_update.
Note that a feed may well have data outstanding even if ctl_xively_feed_update completes successfully as only a subset of outstanding data in the feed may have been sent to Xively.
ctl_xively_feed_has_pending_data returns non-zero if there is outstanding data to push to Xively and zero if there is none.