Removed unused field in loopwavequeue program.

Found by Cppcheck.

test/loopwavequeue.c

@@ -30,7 +30,6 @@ static struct
     SDL_AudioSpec spec;
     Uint8 *sound;               /* Pointer to wave data */
     Uint32 soundlen;            /* Length of wave data */
-    int soundpos;               /* Current play position */
 } wave;