This commit addresses jruby issue #289. The expected behaviour is documented in this rubyspec pull request: https://github.com/rubyspec/rubyspec/pull/153
Apply '-' behaviour to blank padded format directives.
Re-expose and deprecate RubyException.message.
This field is still used by Psych (ruby/psych##292). I re-exposed
it for now but modified all of JRuby to use the accessors so we
aren't getting deprecation warnings. Once the gem is out we can
attempt to hide the field again.