Incorporate hxcpp team feedback:
- Use HX_CSTRING and hxcpp's String class where possible
- Ensure that mutexes are not held when callbacks into Haxe from the debugger
  are made, to ensure that no garbage collection deadlocks can occur
- Don't need to override new and delete to avoid garbage collection issues

Additionally:
- Don't use NULL, for some reason it fails to compile with some compilers (mips)
- Un-DOS-ify GenMacro.hx