perf-utils: Introduce an option for pid_t into parse-options module.

To allow perf command can parse pid_t option from user, this patch add
a parser for pid_t in parse-options module.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
perf-kvm: Introduce an option named '--guestpid' for perf kvm record.

If we use perf kvm record without --guestmount, currently, we can not
pass the pid of guest to perf. Then we can only create a machine for
guest using DEFAULT_GUEST_KERNEL_ID. It is not the pid of guest as
what we want.

This patch introduce an option '--guestpid' to allow user pass a pid
to perf-kvm, then we can create a machine for this guest process.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>