don't include utils.h when it isn't used

src/volume.c

@@ -15,19 +15,20 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
-#include "volume.h"
 
+#include "volume.h"
 #include "conf.h"
 #include "player_control.h"
-#include "utils.h"
 #include "idle.h"
 #include "pcm_utils.h"
 #include "config.h"
 #include "audio.h"
 
 #include <glib.h>
+
 #include <math.h>
 #include <string.h>
+#include <stdlib.h>
 
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "volume"