In 1.8 mode, generator.rb refers to non-existent generator_internal

Since Generator is now built in, strictly speaking "require 'generator'" is not needed. However, old application code (particularly old Ruby 1.8 code) still does require 'generator'. This fails as follows in --1.8 mode:

LoadError: no such file to load – generator_internal
require at org/jruby/RubyKernel.java:1015
(root) at /f/Development/Live/jruby-1.7.0.preview2/lib/ruby/1.8/generator.rb:4

This appears to have its root cause in JRUBY-4218. I gather at some point the internal structure changed, rendering this fix inoperable. In my own copy of 1.7.0.pre2 I have simply modified generator.rb, commenting out the require.