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/opus-1.2.1/celt/x86/celt_lpc_sse.c

@@ -29,6 +29,8 @@
 #include "config.h"
 #endif
 
+#if defined (__i386__) || defined(__x86_64__)
+
 #include <xmmintrin.h>
 #include <emmintrin.h>
 #include <smmintrin.h>
@@ -87,3 +89,4 @@ void celt_fir_sse4_1(const opus_val16 *x,
 }
 
 #endif
+#endif

code/opus-1.2.1/celt/x86/pitch_sse2.c

@@ -29,6 +29,7 @@
 #include "config.h"
 #endif
 
+#if defined (__i386__) || defined(__x86_64__)
 #include <xmmintrin.h>
 #include <emmintrin.h>
 
@@ -93,3 +94,4 @@ opus_val32 celt_inner_prod_sse2(const opus_val16 *x, const opus_val16 *y,
     return sum;
 }
 #endif
+#endif

code/opus-1.2.1/celt/x86/pitch_sse4_1.c

@@ -29,6 +29,8 @@
 #include "config.h"
 #endif
 
+#if defined (__i386__) || defined(__x86_64__)
+
 #include <xmmintrin.h>
 #include <emmintrin.h>
 
@@ -193,3 +195,4 @@ void xcorr_kernel_sse4_1(const opus_val16 * x, const opus_val16 * y, opus_val32
     _mm_storeu_si128((__m128i *)sum, initSum);
 }
 #endif
+#endif

code/opus-1.2.1/celt/x86/vq_sse2.c

@@ -30,6 +30,8 @@
 #include "config.h"
 #endif
 
+#if defined (__i386__) || defined(__x86_64__)
+
 #include <xmmintrin.h>
 #include <emmintrin.h>
 #include "celt_lpc.h"
@@ -215,3 +217,4 @@ opus_val16 op_pvq_search_sse2(celt_norm *_X, int *iy, int K, int N, int arch)
 }
 
 #endif
+#endif

code/opus-1.2.1/silk/x86/VAD_sse.c

@@ -29,6 +29,8 @@
 #include "config.h"
 #endif
 
+#if defined (__i386__) || defined(__x86_64__)
+
 #include <xmmintrin.h>
 #include <emmintrin.h>
 #include <smmintrin.h>
@@ -275,3 +277,4 @@ opus_int silk_VAD_GetSA_Q8_sse4_1(                  /* O    Return value, 0 if s
     RESTORE_STACK;
     return( ret );
 }
+#endif