Fix behavior Hash#eql?

This behavior specification of mruby?

```
> 1.eql?(1.0)
 => false
> [1].eql?([1.0])
 => false
> {a:1}.eql?({a:1.0})
 => true
```

I think it's should be that.

```
> 1.eql?(1.0)
 => false
> [1].eql?([1.0])
 => false
> {a:1}.eql?({a:1.0})
 => false
```