vm_insnhelper.c (vm_call_method): should check ci->me->flag of
a refining method in case the method is private.
[ruby-core:60111] [Bug #9452]
vm_method.c (make_method_entry_refined): set me->flag of a refined
method entry to NOEX_PUBLIC in case the original method is private
and it is refined as a public method. The original flag is stored
in me->def->body.orig_me, so it's OK to make a refined method
entry public. [ruby-core:60111] [Bug #9452]
test/ruby/test_refinement.rb: related tests.