[Truffle] - Moving all code responsible for check the method visibility to RubyMethod class.
[Truffle] - Allowing subclass calls a private method in the superclass
[Truffle] - Allow subclass instances call private method defined in the superclass
Merge branch 'calling-private-methods' of github.com:lucasallan/jruby into lucasallan-calling-private-methods.
[Truffle] Fix merge.