Add specs for Thread{.,#}report_on_exception{=,}
Add specs for Thread{.,#}report_on_exception{=,}

* See #473.

sgarciac/spec,sgarciac/spec,ruby/rubyspec,nobu/rubyspec,ruby/spec,ruby/spec,eregon/rubyspec,ruby/spec,nobu/rubyspec,nobu/rubyspec,sgarciac/spec,ruby/rubyspec,eregon/rubyspec,eregon/rubyspec