Fix executing BigDecimal#round spec twice consecutively
Fix executing BigDecimal#round spec twice consecutively

* Fixes `mspec -R2 library/bigdecimal/round_spec.rb`
* `mode` would get re-assigned and we'd end up with `eval(Integer)`

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