JRuby:Rack::Logger does not provide a zero-argument 'debug' method

[dub357]

This commit added zero-argument versions of logger methods, but it failed to add one for the 'debug' method.
faaabb6

This is causing JRuby-Rack apps containing the following Ruby code:

Rails.logger.debug { "something" }

to throw this error:

wrong number of arguments calling 'debug' (given 0, expected 1)