Update vdltest to include cyclic and native types.

The strategy for both of these is to include them in
vtype_manual.vdl and xtype_manual.vdl, which hold manually
defined types.  These are manually-defined because they are hard
to generate automatically, and easier to debug when defined
manually.  The test entries are still automatically-generated
based on the manual type definitions.

Also fixed some bugs wrt native types, exposed by the new tests.

MultiPart: 3/3
Change-Id: I59d5c3e8a60441c51e346d845fad4e7b916c6252
diff --git a/go/src/v.io/x/sensorlog/internal/sbmodel/sbmodel.vdl.go b/go/src/v.io/x/sensorlog/internal/sbmodel/sbmodel.vdl.go
index fa4a15f..53ebf0a 100644
--- a/go/src/v.io/x/sensorlog/internal/sbmodel/sbmodel.vdl.go
+++ b/go/src/v.io/x/sensorlog/internal/sbmodel/sbmodel.vdl.go
@@ -539,7 +539,7 @@
 	if !x.Start.IsZero() {
 		return false
 	}
-	if x.Interval != time.Duration(0) {
+	if x.Interval != 0 {
 		return false
 	}
 	return true
@@ -575,7 +575,7 @@
 			return err
 		}
 	}
-	if x.Interval != time.Duration(0) {
+	if x.Interval != 0 {
 		if err := enc.NextField("Interval"); err != nil {
 			return err
 		}