Upgrades to Xcode project and Apple Silicon support

- Reorganized Xcode project
- Added missionpack support to Xcode project
- Incorporated changes from MaddTheSane for Apple Silicon support https://github.com/maddthesane/ioq3
- Built SDL 2.0.14 for Apple Siicon, added to existing SDL dylib
- Built SDLMain for Apple Silicon, added to existing libSDL2main.a

code/qcommon/q_platform.h

@@ -156,6 +156,12 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 #define idx64 1
 #define ARCH_STRING "x86_64"
 #define Q3_LITTLE_ENDIAN
+#elif defined __aarch64__
+#define ARCH_STRING "arm64"
+#define Q3_LITTLE_ENDIAN
+#ifndef NO_VM_COMPILED
+#define NO_VM_COMPILED
+#endif
 #endif
 
 #define DLL_EXT ".dylib"