tools/libxc: Wire a featureset through to cpuid policy logic

Later changes (Patch titled "tools/libxc: Use featuresets rather than
guesswork") will cause the cpuid generation logic to seed their
information from a featureset.  This patch adds the infrastructure to
specify a featureset, and will obtain the appropriate defaults from Xen
if omitted.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/python/xen/lowlevel/xc/xc.c

@@ -731,7 +731,7 @@ static PyObject *pyxc_dom_set_policy_cpuid(XcObject *self,
     if ( !PyArg_ParseTuple(args, "i", &domid) )
         return NULL;
 
-    if ( xc_cpuid_apply_policy(self->xc_handle, domid) )
+    if ( xc_cpuid_apply_policy(self->xc_handle, domid, NULL, 0) )
         return pyxc_error_to_exception(self->xc_handle);
 
     Py_INCREF(zero);