capture: add task-id (thread-id) to samples

This could let us do some amount of filtering by threads going
forward if we have that data available to us.

src/libsysprof/sp-perf-source.c

@@ -284,6 +284,7 @@ sp_perf_source_handle_callchain (SpPerfSource                      *self,
                                 sample->time,
                                 cpu,
                                 sample->pid,
+                                sample->tid,
                                 ips,
                                 n_ips);
 }