Add missing VKAPI_ATTR declaration on vulkan layer functions
Add missing VKAPI_ATTR declaration on vulkan layer functions

* Thanks to @Themaister for this fix

TurtleRockStudios/renderdoc_public,baldurk/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,googlestadia/renderdoc,googlestadia/renderdoc,TurtleRockStudios/renderdoc_public,TurtleRockStudios/renderdoc_public,googlestadia/renderdoc,Zorro666/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,baldurk/renderdoc,googlestadia/renderdoc,googlestadia/renderdoc,baldurk/renderdoc,TurtleRockStudios/renderdoc_public,Zorro666/renderdoc,Zorro666/renderdoc,googlestadia/renderdoc,TurtleRockStudios/renderdoc_public,TurtleRockStudios/renderdoc_public