[Graphics.hx] 'default' is a Haxe keyword, needs to be replaced to prevent compile errors

On line 86 of the generated Graphics.hx, the following line causes a compile failure in Haxe:

``@:overload(function (default: DefaultShader, ?options: lua.Table): Shader {})``

``default`` is a reserved keyword to describe getter/setter behavior and switch statement fallback in Haxe. Easiest solution to this would be to generate a different argument name, changing it to ``_default`` solved the issue for me.

Start with the generated Graphics.hx file at line 86 and identify the generator entry point that produces this overload. Reproduce the Haxe compile failure, then verify that regeneration uses a non-reserved argument name such as _default and that the generated binding compiles successfully.

Written by the indexing model from the issue text.