SDL_mixer: fix include guards

From d4befbe74b7e1cd7903f254538efadec0137c372 Mon Sep 17 00:00:00 2001
From: pionere <[EMAIL REDACTED]>
Date: Wed, 15 Dec 2021 10:01:39 +0100
Subject: [PATCH] fix include guards - add include guards to mixer.h - move
 #include "SDL_mixer.h" under the guard of music.h

---
 src/mixer.h | 4 ++++
 src/music.h | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/mixer.h b/src/mixer.h
index 525dc7be..18ab88da 100644
--- a/src/mixer.h
+++ b/src/mixer.h
@@ -18,6 +18,8 @@
      misrepresented as being the original software.
   3. This notice may not be removed or altered from any source distribution.
 */
+#ifndef MIXER_H_
+#define MIXER_H_
 
 /* Locking wrapper functions */
 extern void Mix_LockAudio(void);
@@ -25,4 +27,6 @@ extern void Mix_UnlockAudio(void);
 
 extern void add_chunk_decoder(const char *decoder);
 
+#endif /* MIXER_H_ */
+
 /* vi: set ts=4 sw=4 expandtab: */
diff --git a/src/music.h b/src/music.h
index 4f1b4373..26cc2c4a 100644
--- a/src/music.h
+++ b/src/music.h
@@ -18,11 +18,11 @@
      misrepresented as being the original software.
   3. This notice may not be removed or altered from any source distribution.
 */
-#include "SDL_mixer.h"
-
 #ifndef MUSIC_H_
 #define MUSIC_H_
 
+#include "SDL_mixer.h"
+
 /* Supported music APIs, in order of preference */
 
 typedef enum