Fix Makefile for OSX

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

code/sys/sys_unix.c

@@ -61,7 +61,7 @@ char *Sys_DefaultHomePath(void)
 		if( ( p = getenv( "HOME" ) ) != NULL )
 		{
 			Com_sprintf(homePath, sizeof(homePath), "%s%c", p, PATH_SEP);
-#ifdef MACOS_X
+#ifdef __APPLE__
 			Q_strcat(homePath, sizeof(homePath),
 				"Library/Application Support/");
 
@@ -94,7 +94,7 @@ char *Sys_SteamPath( void )
 
 	if( ( p = getenv( "HOME" ) ) != NULL )
 	{
-#ifdef MACOS_X
+#ifdef __APPLE__
 		char *steamPathEnd = "/Library/Application Support/Steam/SteamApps/common/" STEAMPATH_NAME;
 #else
 		char *steamPathEnd = "/.steam/steam/SteamApps/common/" STEAMPATH_NAME;
@@ -577,7 +577,7 @@ void Sys_ErrorDialog( const char *error )
 	close( f );
 }
 
-#ifndef MACOS_X
+#ifndef __APPLE__
 static char execBuffer[ 1024 ];
 static char *execBufferPointer;
 static char *execArgv[ 16 ];