Make VkNonDispatchableHandle uint64 and bring back vkPreload
Fixes https://github.com/nimgl/nimgl/issues/70 and regenerates vulkan.nim, fixing the incorrect regeneration from this commit: https://github.com/nimgl/vulkan/commit/091ff99e6542f613aadb83c4aad7948299088d93
@lmariscal this PR should fix this issue: https://github.com/nimgl/nimgl/issues/72
The vulkan triangle test is currently broken because vkPreload (and other things) were removed in this commit: https://github.com/nimgl/vulkan/commit/091ff99e6542f613aadb83c4aad7948299088d93
I'm guessing vulkan.nim was regenerated based on an old commit because those things re-appeared when I ran nimble gen again.
BTW, running nimble test still fails because i think it's using the release version of nimgl/vulkan, rather than the one from this repo...