Ruby 1.9+ compatibility.

* Disabled warnings, we don't want it to complain about bugs of generated
  code of Ragel.
* Ruby 1.9 says `#{gi:x}` is a syntax error. This regression is fixed in
  2.0 but it's better to use the more compatible `#{gi :x}`.
* Ruby 1.9 changed `?x` to return a string instead of an integer. This
  caused all import types become nil.