Fix for newer version of Love2D

[pkhead]

This pull request updates the generator to work with newer versions of Love2D, and also to work on Windows.

Here is a comprehensive list of the changes I've made:

1. If it detects you are running on Windows, it uses the mkdir command (instead of mkdir -p) and corrects the path separators in the arguments to the command.
2. The KeyConstant and Scancode enums have been fixed by using a handwritten file instead of automatically generating one. Since those enums have now been fixed, it now uses them instead of using the String type.
3. It now generates an enum abstract (added in a more recent version of Haxe) instead of an @:enum abstract.
4. If it generates an enum identifier that starts with a digit, it prepends an underscore so that it compiles correctly.
5. It escapes special characters for generated enum string values.
6. Union types (those defined as "A or B") generate as a Dynamic.
7. The FFI cdata type is generated as Dynamic.