vks 0.21.0

Vulkan FFI bindings and symbol loader. Vulkan 1.0.59 and all extensions are supported.
Documentation
// Copyright (c) 2017, Dennis Hamester <dennis.hamester@startmail.com>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

macro_rules! cenum {
    (
        $(#[$attr:meta])*
        $name:ident: $ty:ty {
            $(
                $(#[$symbol_attr:meta])*
                const $symbol:ident = $value:expr,
            )*
        }
    ) => (
        $(#[$attr])*
        pub type $name = $ty;

        $(
            $(#[$symbol_attr])*
            pub const $symbol: $name = $value;
        )*
    )
}