mruby/mruby — pull request #1901 by ksss (2014-03-21 03:05:06+00:00)
Title: Fix behavior of Comparable methods when <=> return nil

If `<=>` method return not Integer value,
The ISO spec of some Comparable methods(`<`,`>`,`<=`,`>=`) defined that "the behavior is unspecified".
And _master_, return `false` that time.

But, I think it's should be raise ArgumentError like that.

before

```ruby
> 0.0 <=> nil
=> nil
> 0.0 < nil
=> false
> 0.0 > nil
=> false
> 0.0 == nil
=> false
```

after

```ruby
> 0.0 <=> nil
=> nil
> 0.0 < nil
=> ArgumentError
> 0.0 > nil
=> ArgumentError
> 0.0 == nil
=> false
```