cl: isVargs support defer/go

cl/_testlibc/defer/in.go

@@ -0,0 +1,16 @@
+package main
+
+import "github.com/goplus/llgo/c"
+
+func f(s string) bool {
+	return len(s) > 2
+}
+
+func main() {
+	if s := "hello"; f(s) {
+		defer c.Printf(c.Str("%s\n"), c.AllocaCStr(s))
+	} else {
+		defer c.Printf(c.Str("world\n"))
+	}
+	defer c.Printf(c.Str("bye\n"))
+}