Fix Makefile for OSX

Bump base SDK from 10.5 -> 10.7
Just use the builtin __APPLE__

code/qcommon/net_ip.c

@@ -1268,7 +1268,7 @@ static void NET_AddLocalAddress(char *ifname, struct sockaddr *addr, struct sock
 	}
 }
 
-#if defined(__linux__) || defined(MACOSX) || defined(__BSD__)
+#if defined(__linux__) || defined(__APPLE__) || defined(__BSD__)
 static void NET_GetLocalAddress(void)
 {
 	struct ifaddrs *ifap, *search;