[IR] Added missing getSimplifiedOperand method to WrappedIRClosure

* During recent inlining bug fixing work, I updated WrappedIRClosure
  to add a self variable, but forgot to add getSimplifiedOperand
  method to it. That function has to be implemented by all operands
  that use variables so that variable renaming works correctly.
upgrade to rdoc-4.1.0.preview.3 since the old version was not on rubygems anymore which
made it difficult to keep jruby-dist build pass ITs
[IR] Fix for addInstanceMethod refactoring bug.

* Recent refactoring of DefineInstanceMethodInstr reused new
  visibility of method instead of using original visibility
  when adding it to the method table.

* This bug was replicated in a couple other places -- now fixed.

* This brings IR rubyspec failures/errors  back to previous state.