singleton method_added fixes

[wied03]

Ruby specs - ruby/spec#200

Another RSpec related issue

[elia]

In light of what pointed out by @eregon in ruby/spec#200 (comment) this probably should look like

if (obj.$method_added && !obj.$method_added.$$stub && !obj.$$singleton_of) {
  …
}
else if (obj.$singleton_method_added && !obj.$singleton_method_added.$$stub && obj.$$singleton_of) {
  …
}

and that would probably fix some more ruby specs too… :)

[wied03]

@elia - Implemented your feedback. I've always found it a little odd to grasp the singleton class stuff, but as the code in this PR stands now. Should we be calling $singleton_method_added inside the else on obj instead? Or alternatively, should the else look like this?

else if (singleton_of && singleton_of.$singleton_method_added && !singleton_of.$singleton_method_added.$$stub)

[elia]

Honestly I'm not sure without delving into it again, in doubt skip the else :) 

[wied03]

It passes the rubyspecs either way, which makes me uncomfortable. Maybe I can dig in and find out why.

[eregon]

@wied03 I think your condition above in the comment is good.
obj is a Module or a Class here, which might be confusing naming, and singleton_of is the singleton class' instance AFAIK. singleton_method_added is called on the singleton instance, not a module.
The tests pass because modules/classes respond to singleton_method_added since they are BasicObject.

[wied03]

OK. That makes sense. I pushed that change as well and squashed the commits.