hwcontext_vulkan: fix CreateSemaphore conflict with synchapi.h

Include windows.h to fix it. Normally, it'd be better to include it in
vulkan_functions.h, but I'm reasonably confident nothing else that uses
the Vulkan code will need to include Windows functions and not windows.h.

libavutil/hwcontext_vulkan.c

@@ -19,6 +19,13 @@
 #define VK_NO_PROTOTYPES
 #define VK_ENABLE_BETA_EXTENSIONS
 
+#ifdef _WIN32
+#include <windows.h> /* Included to prevent conflicts with CreateSemaphore */
+#include "compat/w32dlfcn.h"
+#else
+#include <dlfcn.h>
+#endif
+
 #include <unistd.h>
 
 #include "config.h"
@@ -32,12 +39,6 @@
 
 #include "vulkan_loader.h"
 
-#ifdef _WIN32
-#include "compat/w32dlfcn.h"
-#else
-#include <dlfcn.h>
-#endif
-
 #if CONFIG_LIBDRM
 #include <xf86drm.h>
 #include <drm_fourcc.h>