sdl12-compat: Patched to compile on Windows.

SDL Commits
1 
From b9645146f275ffa3c3a04393e06cdd41133ffa5c Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Thu, 24 Jun 2021 15:35:12 -0400
Subject: [PATCH] Patched to compile on Windows.

---
 src/SDL12_compat.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index 753cddf..7a4ed8b 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -2999,10 +2999,10 @@ EventFilter20to12(void *data, SDL_Event *event20)
 
             #if defined(SDL_VIDEO_DRIVER_WINDOWS)
                 SDL_assert(event20->syswm.msg->subsystem == SDL_SYSWM_WINDOWS);
-                msg.hwnd = event20->syswm.msg->hwnd;
-                msg.msg = event20->syswm.msg->msg;
-                msg.wParam = event20->syswm.msg->wParam;
-                msg.lParam = event20->syswm.msg->lParam;
+                msg.hwnd = event20->syswm.msg->win.hwnd;
+                msg.msg = event20->syswm.msg->win.msg;
+                msg.wParam = event20->syswm.msg->win.wParam;
+                msg.lParam = event20->syswm.msg->win.lParam;
             #elif defined(SDL_VIDEO_DRIVER_X11)
                 SDL_assert(event20->syswm.msg->subsystem == SDL_SYSWM_X11);
                 msg.subsystem = SDL12_SYSWM_X11;