Fix: Remove dependency on glibc 2.12 caused by pthread_setname_np

Fix: Remove dependency on glibc 2.12 caused by pthread_setname_np

prctl() can be used to set the same attribute set by
pthread_setname_np, but doesn't introduce a dependency on a newer
glibc. Using prctl(PR_SET_NAME) introduces a soft dependency on
Linux 2.6.9. However, the worker won't fail to launch if the call
fails as it is set out of convenience (debugger output).

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>