This implements the wrapper around libxl_domain_create_new(). With
the previous changes, it's now possible to create a domain using the
golang bindings (although not yet to unpause it or harvest it after it
shuts down).
Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Nick Rosbrook <rosbrookn@ainfosec.com>