vulkan: SDL_Vulkan_CreateSurface now returns the usual int (0=ok, -1=error).

Fixes #10091.

test/testvulkan.c

@@ -259,10 +259,7 @@ static void loadInstanceFunctions(void)
 
 static void createSurface(void)
 {
-    if (!SDL_Vulkan_CreateSurface(vulkanContext->window,
-                                  vulkanContext->instance,
-                                  NULL,
-                                  &vulkanContext->surface)) {
+    if (SDL_Vulkan_CreateSurface(vulkanContext->window, vulkanContext->instance, NULL, &vulkanContext->surface) < 0) {
         vulkanContext->surface = VK_NULL_HANDLE;
         SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "SDL_Vulkan_CreateSurface(): %s\n", SDL_GetError());
         quit(2);