Fixes for -fno-common
From AUR: https://aur.archlinux.org/cgit/aur.git/tree/mirrormagic-3.0.0-variables-scope.patch?h=mirrormagic

Index: src/main.c
--- src/main.c.orig
+++ src/main.c
@@ -69,7 +69,7 @@ short			ExplodeDelay[MAX_LEV_FIELDX][MAX_LEV_FIELDY];
 int			RunnerVisit[MAX_LEV_FIELDX][MAX_LEV_FIELDY];
 int			PlayerVisit[MAX_LEV_FIELDX][MAX_LEV_FIELDY];
 
-int			GfxFrame[MAX_LEV_FIELDX][MAX_LEV_FIELDY];
+extern int		GfxFrame[MAX_LEV_FIELDX][MAX_LEV_FIELDY];
 int 			GfxRandom[MAX_LEV_FIELDX][MAX_LEV_FIELDY];
 int 			GfxElement[MAX_LEV_FIELDX][MAX_LEV_FIELDY];
 int			GfxAction[MAX_LEV_FIELDX][MAX_LEV_FIELDY];
@@ -138,7 +138,7 @@ struct LevelInfo	level, level_template;
 struct PlayerInfo	stored_player[MAX_PLAYERS], *local_player = NULL;
 struct HiScore		highscore[MAX_SCORE_ENTRIES];
 struct TapeInfo		tape;
-struct SetupInfo	setup;
+extern struct SetupInfo	setup;
 struct GameInfo		game;
 struct GlobalInfo	global;
 struct BorderInfo	border;
