XML definitions for guest NUMA and parsing routines

XML definitions for guest NUMA and parsing routines

This patch adds XML definitions for guest NUMA specification and contains
routines to parse the same. The guest NUMA specification looks like this:

<cpu>
        ...
        <topology sockets='2' cores='4' threads='2'/>
        <numa>
                <cell cpus='0-7' memory='512000'/>
                <cell cpus='8-15' memory='512000'/>
        </numa>
        ...
</cpu>

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>