SDL: Fixed building with older Windows SDK (c24b3)

From c24b33d8d946a4e6af78604fd1c562f4eff72478 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Thu, 28 Dec 2023 15:14:34 -0800
Subject: [PATCH] Fixed building with older Windows SDK

---
 src/video/windows/SDL_windowsvideo.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/video/windows/SDL_windowsvideo.h b/src/video/windows/SDL_windowsvideo.h
index 2be8eba3eb08..b5a380038d3d 100644
--- a/src/video/windows/SDL_windowsvideo.h
+++ b/src/video/windows/SDL_windowsvideo.h
@@ -52,6 +52,10 @@
 
 #include "SDL_windowswindow.h"
 
+#ifndef USER_DEFAULT_SCREEN_DPI
+#define USER_DEFAULT_SCREEN_DPI 96
+#endif
+
 #if WINVER < 0x0601
 /* Touch input definitions */
 #define TWF_FINETOUCH 1