SDL: Added header for SDL_ThreadID type

From 04bb105d09180f37e3e8815ff650be81d3dd111b Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Fri, 27 Sep 2024 08:16:49 -0700
Subject: [PATCH] Added header for SDL_ThreadID type

---
 include/SDL3/SDL_mutex.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/SDL3/SDL_mutex.h b/include/SDL3/SDL_mutex.h
index 78b44aaac2041..03cb80cfb6754 100644
--- a/include/SDL3/SDL_mutex.h
+++ b/include/SDL3/SDL_mutex.h
@@ -29,6 +29,7 @@
  */
 
 #include <SDL3/SDL_stdinc.h>
+#include <SDL3/SDL_atomic.h>
 #include <SDL3/SDL_error.h>
 #include <SDL3/SDL_thread.h>