[Issue #14] fixed: multiple sounds cannot played at the same time (kinghtt)

- this is a simple hackfix which should work most of the time

sound.c

@@ -48,6 +48,10 @@ static BOOL  g_fUseWav = FALSE;
 INT          g_iVolume  = SDL_MIX_MAXVOLUME * 0.1;
 #endif
 
+#ifdef PAL_CLASSIC
+int          g_iCurrChannel = 0;
+#endif
+
 typedef struct tagSNDPLAYER
 {
    FILE                     *mkf;

sound.h

@@ -72,7 +72,12 @@ SOUND_PlayCDA(
    INT    iNumTrack
 );
 
+#ifdef PAL_CLASSIC
+extern int g_iCurrChannel;
+#define SOUND_Play(i) SOUND_PlayChannel((i), (g_iCurrChannel ^= 1))
+#else
 #define SOUND_Play(i) SOUND_PlayChannel((i), 0)
+#endif
 
 extern BOOL       g_fNoSound;
 extern BOOL       g_fNoMusic;