add void casts to suppress "result unused" warnings (clang)

NEWS

 ver 0.16.1 (2010/??/??)
 * audio_check: fix parameter in prototype
+* add void casts to suppress "result unused" warnings (clang)
 * decoder:
   - mad: work around build failure on Solaris
 * output:

src/output_thread.c

@@ -303,7 +303,7 @@ ao_wait(struct audio_output *ao)
 		GTimeVal tv;
 		g_get_current_time(&tv);
 		g_time_val_add(&tv, delay * 1000);
-		g_cond_timed_wait(ao->cond, ao->mutex, &tv);
+		(void)g_cond_timed_wait(ao->cond, ao->mutex, &tv);
 
 		if (ao->command != AO_COMMAND_NONE)
 			return false;

src/poison.h

@@ -47,7 +47,7 @@ poison_noaccess(void *p, size_t length)
 	memset(p, 0x01, length);
 
 #ifdef HAVE_VALGRIND_MEMCHECK_H
-	VALGRIND_MAKE_MEM_NOACCESS(p, length);
+	(void)VALGRIND_MAKE_MEM_NOACCESS(p, length);
 #endif
 #endif
 }
@@ -68,7 +68,7 @@ poison_undefined(void *p, size_t length)
 	memset(p, 0x02, length);
 
 #ifdef HAVE_VALGRIND_MEMCHECK_H
-	VALGRIND_MAKE_MEM_UNDEFINED(p, length);
+	(void)VALGRIND_MAKE_MEM_UNDEFINED(p, length);
 #endif
 #endif
 }