Haxe 3 support

Trying to build the docs with `haxe -xml` was failing on Haxe 3.  This change allows that command to run without error, however I have done no additional testing.  If you could advise me if you have any tests available I will check this against them.

I will be trying to use this with [flambe](https://github.com/aduros/flambe), and if any other issues arise I will add them to the pull request.