Panic in JSON.stringify of struct with anonymous pointer field

[ale-rinaldi]

If I have a struct with an anonymous pointer field, I pass it to the VM, and try to JSON.stringify it, I get a panic.

An easy way to reproduce is running this code:

package main

import (
	"github.com/robertkrimen/otto"
)

func main() {
	type Test struct {
		Value string
	}

	type PtrTest struct {
		*Test
	}

	testItem := Test{
		Value: "A test value",
	}

	ptrTestItem := PtrTest{
		Test: &testItem,
	}

	jsCode := `
		console.log(JSON.stringify(testVariable));
	`

	vm := otto.New()
	vm.Set("testVariable", ptrTestItem)
	vm.Run(jsCode)
}

[ale-rinaldi]

Pull request #370 seems to solve the issue with no apparent regressions, but since I don't know why the f.Anonymous check was in place, I'm not sure that's the right solution.