Returned Proc of Symbol#to_proc should raise an ArgumentError when calling #call without receiver parameter

MRI

* ruby 1.8.7 (2012-10-12 patchlevel 371)
* ruby 1.9.3p392 (2013-02-22 revision 39386)

```ruby
:object_id.to_proc.call #=> ArgumentError: no receiver given
:DUMMY.to_proc.call     #=> ArgumentError: no receiver given
```

Rubinius

* rubinius 2.0.0.rc1 (1.8.7 aacddf7e yyyy-mm-dd JI)
* rubinius 2.0.0.rc1 (1.9.3 aacddf7e yyyy-mm-dd JI)

```ruby
:object_id.to_proc.call #=> 26
:DUMMY.to_proc.call     #=> NoMethodError: undefined method `DUMMY' on nil:NilClass.
```