fix missing @details under ruby2 due to change in respond_to? behavior

The newrelic instrumentation currently breaks rails applications running under ruby 2.0 release candidates, due to this change in behavior of 'respond_to?':
http://tenderlovemaking.com/2012/09/07/protected-methods-and-ruby-2-0.html

This patch passes in 'true' as the second argument to 'respond_to?' to fix the issue under ruby2 (and should be innocuous under ruby versions < 2).