Haxe Ruby Target

Hi! This is a fork of Haxe that adds a ruby target. The fork is already more than enough for my purposes (translating https://github.com/paulfitz/coopyhx), but your mileage will do that thing that mileage does. There is lots done, and lots still to do. I do plan to submit a pull request once the code passes most of Haxe's unit tests.