lib: remove RUSAGE_T from struct thread

* thread.c: It's only temporarily used in thread_call() to calculate the
  diffs. Saves 80 bytes per copy.

Signed-off-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
2 files changed