work around ruby-debug injecting #start into Kernel on JRuby
changelog
Fixup the spec to work regardless of which solution we wind up with.

The original spec was focused on the exact fix that was originally put
in place, but we may wind up changing to an alternate fix that
would not be tested by the spec as it was.
restore original deprecation formatter
check that formatter understands notification
remove (now unecessary) as_null_object calls as they interfer with the check for listener understanding
Merge pull request #967 from rspec/quick_fix_for_deprecation_formatter_on_jruby

Properly base #966 off 2-14-maintenance