test_rubyopts_rubygems_cleared_in_child test failure w/ patch

The test for test_rubyopts_rubygems_cleared_in_child fails when run in 1.9 mode because rubygems is now packaged by default, and the require is no longer necessary:

"Ruby 1.9
The default Ruby 1.9 package now includes RubyGems by default on most platforms (presently Debian based systems split this out into a separate package). This means that on Ruby 1.9 and above, you will not need to require 'rubygems' in order to load gem libraries."

Source: http://docs.rubygems.org/read/chapter/3

This patch fixes this by using one of the standard library packages, benchmark, to properly test the environment clearing in the child process.