Allow for user song lists

.gitignore

@@ -73,3 +73,6 @@ __pycache__
 
 # prerequisites for updating ChibiOS
 /util/fmpp*
+
+# Allow to exist but don't include it in the repo
+user_song_list.h

quantum/audio/song_list.h

@@ -20,6 +20,12 @@
 
 #include "musical_notes.h"
 
+#if __GNUC__ > 5 // don't use for older gcc compilers since check isn't supported.
+# if __has_include("user_song_list.h")
+# include "user_song_list.h"
+# endif // if file exists
+#endif // __GNUC__
+
 #define NO_SOUND
 
 /* Ode to Joy
@@ -146,44 +152,126 @@
  * proof of permission to use them, or public domain status.
  */
 
-#define CLOSE_ENCOUNTERS_5_NOTE
-#define DOE_A_DEER
-#define IN_LIKE_FLINT
-#define IMPERIAL_MARCH
-#define BASKET_CASE
-#define COIN_SOUND
-#define ONE_UP_SOUND
-#define SONIC_RING
-#define ZELDA_PUZZLE
-#define ZELDA_TREASURE
-#define OVERWATCH_THEME
-#define MARIO_THEME
-#define MARIO_GAMEOVER
-#define MARIO_MUSHROOM
-#define E1M1_DOOM
-#define DISNEY_SONG
-#define NUMBER_ONE
-#define CABBAGE_SONG
-#define OLD_SPICE
-#define VICTORY_FANFARE_SHORT
-#define ALL_STAR
-#define RICK_ROLL
-#define FF_PRELUDE
-#define TO_BOLDLY_GO
-#define KATAWARE_DOKI
-#define MEGALOVANIA
-#define MICHISHIRUBE
-#define LIEBESLEID
-#define MELODIES_OF_LIFE
-#define EYES_ON_ME
-#define SONG_OF_THE_ANCIENTS
-#define NIER_AMUSEMENT_PARK
-#define COPIED_CITY
-#define VAGUE_HOPE_COLD_RAIN
-#define KAINE_SALVATION
-#define WEIGHT_OF_THE_WORLD
-#define ISABELLAS_LULLABY
-#define TERRAS_THEME
-#define RENAI_CIRCULATION
-#define PLATINUM_DISCO
-#define LP_NUMB
+#ifndef CLOSE_ENCOUNTERS_5_NOTE
+# define CLOSE_ENCOUNTERS_5_NOTE
+#endif
+#ifndef DOE_A_DEER
+# define DOE_A_DEER
+#endif
+#ifndef IN_LIKE_FLINT
+# define IN_LIKE_FLINT
+#endif
+#ifndef IMPERIAL_MARCH
+# define IMPERIAL_MARCH
+#endif
+#ifndef BASKET_CASE
+# define BASKET_CASE
+#endif
+#ifndef COIN_SOUND
+# define COIN_SOUND
+#endif
+#ifndef ONE_UP_SOUND
+# define ONE_UP_SOUND
+#endif
+#ifndef SONIC_RING
+# define SONIC_RING
+#endif
+#ifndef ZELDA_PUZZLE
+# define ZELDA_PUZZLE
+#endif
+#ifndef ZELDA_TREASURE
+# define ZELDA_TREASURE
+#endif
+#ifndef OVERWATCH_THEME
+# define OVERWATCH_THEME
+#endif
+#ifndef MARIO_THEME
+# define MARIO_THEME
+#endif
+#ifndef MARIO_GAMEOVER
+# define MARIO_GAMEOVER
+#endif
+#ifndef MARIO_MUSHROOM
+# define MARIO_MUSHROOM
+#endif
+#ifndef E1M1_DOOM
+# define E1M1_DOOM
+#endif
+#ifndef DISNEY_SONG
+# define DISNEY_SONG
+#endif
+#ifndef NUMBER_ONE
+# define NUMBER_ONE
+#endif
+#ifndef CABBAGE_SONG
+# define CABBAGE_SONG
+#endif
+#ifndef OLD_SPICE
+# define OLD_SPICE
+#endif
+#ifndef VICTORY_FANFARE_SHORT
+# define VICTORY_FANFARE_SHORT
+#endif
+#ifndef ALL_STAR
+# define ALL_STAR
+#endif
+#ifndef RICK_ROLL
+# define RICK_ROLL
+#endif
+#ifndef FF_PRELUDE
+# define FF_PRELUDE
+#endif
+#ifndef TO_BOLDLY_GO
+# define TO_BOLDLY_GO
+#endif
+#ifndef KATAWARE_DOKI
+# define KATAWARE_DOKI
+#endif
+#ifndef MEGALOVANIA
+# define MEGALOVANIA
+#endif
+#ifndef MICHISHIRUBE
+# define MICHISHIRUBE
+#endif
+#ifndef LIEBESLEID
+# define LIEBESLEID
+#endif
+#ifndef MELODIES_OF_LIFE
+# define MELODIES_OF_LIFE
+#endif
+#ifndef EYES_ON_ME
+# define EYES_ON_ME
+#endif
+#ifndef SONG_OF_THE_ANCIENTS
+# define SONG_OF_THE_ANCIENTS
+#endif
+#ifndef NIER_AMUSEMENT_PARK
+# define NIER_AMUSEMENT_PARK
+#endif
+#ifndef COPIED_CITY
+# define COPIED_CITY
+#endif
+#ifndef VAGUE_HOPE_COLD_RAIN
+# define VAGUE_HOPE_COLD_RAIN
+#endif
+#ifndef KAINE_SALVATION
+# define KAINE_SALVATION
+#endif
+#ifndef WEIGHT_OF_THE_WORLD
+# define WEIGHT_OF_THE_WORLD
+#endif
+#ifndef ISABELLAS_LULLABY
+# define ISABELLAS_LULLABY
+#endif
+#ifndef TERRAS_THEME
+# define TERRAS_THEME
+#endif
+#ifndef RENAI_CIRCULATION
+# define RENAI_CIRCULATION
+#endif
+#ifndef PLATINUM_DISCO
+# define PLATINUM_DISCO
+#endif
+#ifndef LP_NUMB
+# define LP_NUMB
+#endif