sdl12-compat: Hook up SDL_GL_SetAttribute(SDL_GL_SWAP_CONTROL, ...)

SDL Commits
1 
From 012e2efff9b7941759abc2c68a1dd1f337829338 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Wed, 2 Jun 2021 22:41:03 -0400
Subject: [PATCH] Hook up SDL_GL_SetAttribute(SDL_GL_SWAP_CONTROL, ...)

---
 src/SDL12_compat.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index c24640f..258397e 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -3797,6 +3797,8 @@ SDL_SetVideoMode(int width, int height, int bpp, Uint32 flags12)
             VideoSurface12->flags |= SDL12_OPENGLBLIT;
         }
 
+        SDL20_GL_SetSwapInterval(SwapInterval);
+
     } else {
         /* always use a renderer for non-OpenGL windows. */
         const char *vsync_env = SDL20_getenv("SDL12COMPAT_SYNC_TO_VBLANK");