Add VK_NN_vi_surface extension

[Rua]

I followed the examples of other surface extensions for this one, so hopefully it's good as-is. I was not sure whether the function names should have _nn at the end or not. create_xlib_surface doesn't end in _khr but create_mac_os_surface_mvk does have the _mvk. My own preference would be without the suffix, since it's already implicit in the module and struct name.

[MarijnS95]

I was not sure whether the function names should have _nn at the end or not. create_xlib_surface doesn't end in _khr but create_mac_os_surface_mvk does have the _mvk. My own preference would be without the suffix, since it's already implicit in the module and struct name.

Fully agree; perhaps a followup patch should remove it from macos_surface and ios_surface. We're allowed to version-wise, though some projects might not like us for it :D