golang/xenlight: define KeyValueList as empty struct

Define KeyValueList as empty struct as there is currently no reason for
this type to be available in the Go package.

Implement fromC and toC functions as no-ops.

Signed-off-by: Nick Rosbrook <rosbrookn@ainfosec.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>

tools/golang/xenlight/xenlight.go

@@ -202,6 +202,16 @@ func (chwcap C.libxl_hwcap) toGo() (ghwcap Hwcap) {
 	return
 }
 
+// KeyValueList represents a libxl_key_value_list.
+//
+// Represented as an empty struct for now, as there is no
+// apparent need for this type to be exposed through the
+// Go package.
+type KeyValueList struct{}
+
+func (kvl KeyValueList) fromC(ckvl *C.libxl_key_value_list) error      { return nil }
+func (kvl KeyValueList) toC() (ckvl C.libxl_key_value_list, err error) { return }
+
 // typedef struct {
 //     uint32_t size;          /* number of bytes in map */
 //     uint8_t *map;