Fix Makefile for OSX

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

code/sys/sys_local.h

@@ -44,7 +44,7 @@ unsigned int CON_LogSize( void );
 unsigned int CON_LogWrite( const char *in );
 unsigned int CON_LogRead( char *out, unsigned int outSize );
 
-#ifdef MACOS_X
+#ifdef __APPLE__
 char *Sys_StripAppBundle( char *pwd );
 #endif