Check if include of vk_platform.h is required

[SaschaWillems]

All chapters explicitly include "vulkan/vk_platform.h". We should check if that's really required, as you usually don't explicitly include headers like this. They should instead by implicitly included via the "main" Vulkan header. Same for GLFW_INCLUDE_VULKAN, which seems to be superfluous.

[SaschaWillems]

Just tested this with chapter 31 (compute shader). Code compiles fine (Windows) when removing the "vulkan/vk_platform.h" include. So we prob. don't need that unit at all? After all, vulkan_raii implicitly includes vulkan.h, which includes vk_platform.h.