A Vulkan layer to display information about the running application
using an overlay.

To turn on the layer run :
```
VK_INSTANCE_LAYERS=VK_LAYER_MESA_overlay /path/to/my_vulkan_app
```

List the available statistics :
```
VK_INSTANCE_LAYERS=VK_LAYER_MESA_overlay VK_LAYER_MESA_OVERLAY_STATS=help /path/to/my_vulkan_app
```

Turn on some statistics :
```
VK_INSTANCE_LAYERS=VK_LAYER_MESA_overlay VK_LAYER_MESA_OVERLAY_STATS=submit,draw,pipeline-graphics /path/to/my_vulkan_app
```

Position the layer :
```
VK_INSTANCE_LAYERS=VK_LAYER_MESA_overlay VK_LAYER_MESA_OVERLAY_STATS=submit,draw,pipeline-graphics VK_LAYER_MESA_OVERLAY_POSITION=top-right /path/to/my_vulkan_app
```