JIT-compile methods named 'none'.

`jruby.jit.exclude` is set by default to "none", so methods named `none` [won't be JIT-compiled](https://github.com/jruby/jruby/blob/master/core/src/main/java/org/jruby/compiler/JITCompiler.java#L246).

How to reproduce:

```
$ pry
[1] pry(main)> def none
[1] pry(main)* end  
=> nil
[2] pry(main)> 100_000.times { |_| none }
2013-08-14T22:30:28.399+03:00: JITCompiler: skipping method: Object#none:Object.none at (pry):1
=> 100000

```