sdl12-compat: Fixed function signatures.

SDL Commits
1 
From 6aaacd63a965ea2f2bc918d5774e0b3247a26890 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 1 Mar 2021 21:11:05 -0500
Subject: [PATCH] Fixed function signatures.

---
 src/SDL12_compat.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index 9474575..33379be 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -4545,17 +4545,20 @@ SDL_OpenAudio(SDL_AudioSpec *want, SDL_AudioSpec *obtained)
 
 /* !!! FIXME: these are just stubs for now, but Sam thinks that maybe these
 were added at Loki for Heavy Gear 2's UI. They just make GL calls. */
-void SDL_GL_Lock()
+DECLSPEC void SDLCALL
+SDL_GL_Lock()
 {
     FIXME("write me");
 }
 
-void SDL_GL_UpdateRects(int numrects, SDL_Rect *rects)
+DECLSPEC void SDLCALL
+SDL_GL_UpdateRects(int numrects, SDL_Rect *rects)
 {
     FIXME("write me");
 }
 
-void SDL_GL_Unlock()
+DECLSPEC void SDLCALL
+SDL_GL_Unlock()
 {
     FIXME("write me");
 }