This patch contains an empty Vulkan shell with only GetProcAddr implemented

Initial version of the VulkanAPI, empty and unimplemented.
Successfully builds vk_swiftshader.dll for all platforms/configuration in Visual Studio.

To test using dEQP:
- Edit environment variables
	- Define VK_ICD_FILENAMES to <SwiftShader's source directory>\src\Vulkan\vk_swiftshader_icd.json
- If the location of vk_swiftshader.dll you're using is different than the one specified in
  src\Vulkan\vk_swiftshader_icd.json, modify it to point to the vk_swiftshader.dll file you want to use

Bug b/116336664

Change-Id: I560b53c3e4340b9c5ccd244a6693ff2f9f994a6f
Reviewed-on: https://swiftshader-review.googlesource.com/20788Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>