blktrace blkreplay: convert to use a dynamic cpu_set_t

Some distros have changed CPU_SETSIZE in glibc to 4096 since that matches
the NR_CPUS in the linux kernel config file.  Some distros have decided to
leave CPU_SETSIZE at 1024. This is a problem if you want to run that distro
on a very large machine.

CPU_SETSIZE is use by the struct cpu_set_t.  This means you to deal with cpus
greater the 1024 you must use the dynamic cpu sets, which involves converting
from things like CPU_SET to CPU_SET_S.

Cc: Jens Axboe <axboe@kernel.dk>
Modified by Jens to fix the CPU_{SET,ZERO}_S pointer mixup.

Signed-off-by: Nathan Zimmer <nzimmer@sgi.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>