Fix build with -fno-common

Index: play-s3m.c
--- play-s3m.c.orig
+++ play-s3m.c
@@ -8,7 +8,7 @@
 #include "play-s3m.h"	/*(playS3m)*/
 #include "mem.h"	/*(memXXX)*/
 
-struct {
+static struct {
     const u8 *p0;
     const u8 *songName;
     i15x ordNum;
