Per-domain vNUMA initialization.

domctl hypercall is used to set vNUMA topology
per domU during domain build time.

Changes since v1:

- uses hypercall_bounce_pre/post to initialize pointers before issuing
domctl hypercall;
- fixed types to unsigned int;

Signed-off-by: Elena Ufimtseva <ufimtseva@gmail.com>