Remove the functionality provided by -r option

Memcached should not need to implement the functionality
to increase/decrease the core file size. It should be set in
the parent process before starting memcached.

Change-Id: Idaa0ebfc9f4acccb6b12e62ce2c0029ad0885e40
Reviewed-on: http://review.couchbase.org/33077
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>