[Vulkan] Redundant preprocessor conditionals
Tried to generate Vulkan loader with all extensions.
Everything works, but it looks ugly.

```cpp
#if defined(VK_USE_PLATFORM_XLIB_KHR)

#endif

#if defined(VK_USE_PLATFORM_XLIB_KHR)

#endif

#if defined(VK_USE_PLATFORM_XLIB_XRANDR_EXT)

#endif

#if defined(VK_USE_PLATFORM_WAYLAND_KHR)

#endif

#if defined(VK_USE_PLATFORM_WAYLAND_KHR)

#endif

#if defined(VK_USE_PLATFORM_WIN32_KHR)

#endif

#if defined(VK_USE_PLATFORM_WIN32_KHR)

#endif

#if defined(VK_USE_PLATFORM_WIN32_KHR)

#endif

#if defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR)

#endif

#if defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR)

#endif

#if defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR)

#endif

#if defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR) || defined(VK_USE_PLATFORM_WIN32_KHR)

#endif

#if defined(VK_USE_PLATFORM_XCB_KHR)

#endif

#if defined(VK_USE_PLATFORM_XCB_KHR)

#endif

#if defined(VK_USE_PLATFORM_XCB_KHR)

#endif

#if defined(VK_USE_PLATFORM_DIRECTFB_EXT)

#endif

#if defined(VK_USE_PLATFORM_DIRECTFB_EXT)

#endif

#if defined(VK_USE_PLATFORM_FUCHSIA) || defined(VK_USE_PLATFORM_FUCHSIA) || defined(VK_USE_PLATFORM_FUCHSIA) || defined(VK_USE_PLATFORM_FUCHSIA)

#endif

#if defined(VK_USE_PLATFORM_GGP)

#endif

#if defined(VK_USE_PLATFORM_GGP)

#endif

#if defined(VK_USE_PLATFORM_SCREEN_QNX)

#endif

#if defined(VK_USE_PLATFORM_SCREEN_QNX)

#endif
```
