SDL: Rename SDL_main_impl.h include guard to match the filename

From 59a70d568d43ecfb0a1e291874a4409fec9a3a87 Mon Sep 17 00:00:00 2001
From: Zack Middleton <[EMAIL REDACTED]>
Date: Sat, 17 Dec 2022 23:13:25 -0600
Subject: [PATCH] Rename SDL_main_impl.h include guard to match the filename

---
 include/SDL3/SDL_main_impl.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/SDL3/SDL_main_impl.h b/include/SDL3/SDL_main_impl.h
index 38481518920b..230fea9a9dca 100644
--- a/include/SDL3/SDL_main_impl.h
+++ b/include/SDL3/SDL_main_impl.h
@@ -19,8 +19,8 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 
-#ifndef SDL_main_windows_h_
-#define SDL_main_windows_h_
+#ifndef SDL_main_impl_h_
+#define SDL_main_impl_h_
 
 #if !defined(SDL_main_h_)
 #error "This header should not be included directly, but only via SDL_main.h!"
@@ -197,4 +197,4 @@ int main(int argc, char *argv[])
 
 #endif /* SDL_MAIN_HANDLED */
 
-#endif /* SDL_main_windows_h_ */
+#endif /* SDL_main_impl_h_ */