Add a package with bindings for VulkanMemoryAllocator

[jclc]

The Vulkan spec doesn't require the driver to handle memory allocation, leaving the user with the responsibility to deal with the memory management. For most use cases however, the VulkanMemoryAllocator library is sufficient. Would be nice having it included with the Vulkan bindings, perhaps under a subpackage called vma.

[jclc]

I have some preliminary work done at https://github.com/jclc/vulkan/tree/vma. This might be a little tricky since while the header defines the interface in C, the implementation is in C++.

[xlab]

@jclc what do you think about separating this into standalone repo? E.g. https://github.com/vulkan-go/vma The project is too big to add side-projects in the root..

Also, no need to fork.

[jclc]

Probably a good idea. I'm still studying how to use c-for-go. One question I have is how to make vma use the Vulkan types from this repository? Will that require some post-processing that adds an import to the file and replaces all identifiers beginning with Vk with vk., or can it be done directly in the generator?

[xlab]

@jclc usually by hand, using helpers that accept unsafe.Pointerss and wrap it in the "local" type. Need some examples..

[jclc]

There are now (mostly) functional bindings at https://github.com/vulkan-go/vma