Fix build problems under OS X

code/client/snd_mix.c

@@ -22,7 +22,7 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 // snd_mix.c -- portable code to mix sounds for snd_dma.c
 
 #include "snd_local.h"
-#if idppc_altivec
+#if idppc_altivec && !defined(MACOS_X)
 #include <altivec.h>
 #endif