SDL_rtf: fix build of showrtf test program

From 334de791df1622b0d9a60bc2d4fc0cefa7eed26e Mon Sep 17 00:00:00 2001
From: Ozkan Sezer <[EMAIL REDACTED]>
Date: Thu, 2 Dec 2021 23:40:24 +0300
Subject: [PATCH] fix build of showrtf test program

---
 showrtf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/showrtf.c b/showrtf.c
index 0969e8c..9ef4df7 100644
--- a/showrtf.c
+++ b/showrtf.c
@@ -25,6 +25,7 @@
 
 #include <stdlib.h>
 #include <string.h>
+#include <stdio.h>
 
 #include "SDL.h"
 #include "SDL_ttf.h"