ASAN only shows some internal thread designation on reports, e.g.:

```
WRITE of size 8 at 0x7b749d2d9190 thread T49
```

which is useless. We should add this capability to Linux. JDK-7102541 added support for thread names in gdb, which uses `_pthread_setname_np`, but for some reason, these names don't show up in ASAN. If we set them with `prctl`, they do show up. I originally assumed glibc's version of `_pthread_setname_np` uses `prctl`, but apparently it doesn't.