do warning suppression for soundlib vars another way

Instead of introducing a bunch of preprocessor #ifdef blocks,
this approach is less-intrusive.

include/sndprocs.h

@@ -352,7 +352,8 @@ SoundAchievement(0, sa2_xpleveldown, level);
         || defined(SND_LIB_SOUND_ESCCODES) || defined(SND_LIB_VISSOUND) \
         || defined(SND_LIB_WINDSOUND) || defined(SND_LIB_MACSOUND)
 
-#define SND_LIB_INTEGRATED   /* shortcut for conditional code in other files */
+/* shortcut for conditional code in other files */
+#define SND_LIB_INTEGRATED
 
 #define Play_usersound(filename, vol, idx) \
     do {                                                                      \
@@ -395,14 +396,22 @@ SoundAchievement(0, sa2_xpleveldown, level);
 
 /*  void (*sound_achievement)(schar, schar, int32_t); */
 
-#else
+#ifdef SOUNDLIBONLY
+#undef SOUNDLIBONLY
+#endif
+#define SOUNDLIBONLY
+#else  /*  NO SOUNDLIB SELECTED AFTER THIS */
 #ifdef SND_LIB_INTEGRATED
-#undef  SND_LIB_INTEGRATED
+#undef SND_LIB_INTEGRATED
 #endif
 #define Play_usersound(filename, vol, idx)
 #define Soundeffect(seid, vol)
 #define Hero_playnotes(instrument, str, vol)
 #define SoundAchievement(arg1, arg2, avals)
+#ifdef SOUNDLIBONLY
+#undef SOUNDLIBONLY
+#endif
+#define SOUNDLIBONLY UNUSED
 #endif
 
 #endif /* SNDPROCS_H */

src/mthrowu.c

@@ -1235,13 +1235,11 @@ hit_bars(
         }
     } else {
         if (!Deaf) {
-#ifdef SND_LIB_INTEGRATED
-            static enum sound_effect_entries se[] = {
+            static enum sound_effect_entries se[] SOUNDLIBONLY = {
                 se_zero_invalid,
                 se_bars_whang, se_bars_whap, se_bars_flapp,
                 se_bars_clink, se_bars_clonk
             };
-#endif
             static const char *const barsounds[] = {
                 "", "Whang", "Whap", "Flapp", "Clink", "Clonk"
             };

src/music.c

@@ -846,7 +846,7 @@ do_play_instrument(struct obj* instr)
 }
 
 enum instruments
-obj_to_instr(struct obj *obj) {
+obj_to_instr(struct obj *obj SOUNDLIBONLY) {
     enum instruments ret_instr = ins_no_instrument;
 
 #if defined(SND_LIB_INTEGRATED)
@@ -886,8 +886,6 @@ obj_to_instr(struct obj *obj) {
             ret_instr = ins_melodic_tom;
             break;
     }
-#else
-    nhUse(obj);
 #endif
     return ret_instr;
 }