gnet_stats_copy_app — copy application specific statistics into statistics TLV
int gnet_stats_copy_app (struct gnet_dump * d, void * st, int len);
Appends the application sepecific statistics to the top level TLV created by
gnet_stats_start_copy and remembers the data for XSTATS if the dumping
handle is in backward compatibility mode.
Returns 0 on success or -1 with the statistic lock released if the room in the socket buffer was not sufficient.