[PATCH] Add flag to dump the labels when the program terminates.

[Peter Collingbourne]

LGTM

================
Comment at: test/dfsan/dump_labels.c:58
@@ +57,3 @@
+    // This should not happen if the program correctly runs out of labels.
+    fprintf(stderr, "l %d\n", l);
+
----------------
You could add a `CHECK-OOL-NOT` line to make sure this line is not printed.

http://reviews.llvm.org/D6306