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

misc/xcode/ioquake3-Info.plist

@@ -6,8 +6,6 @@
 	<string>en</string>
 	<key>CFBundleExecutable</key>
 	<string>${EXECUTABLE_NAME}</string>
-	<key>CFBundleIconFile</key>
-	<string>quake3_flat</string>
 	<key>CFBundleIdentifier</key>
 	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
 	<key>CFBundleInfoDictionaryVersion</key>
@@ -21,7 +19,7 @@
 	<key>CFBundleSignature</key>
 	<string>????</string>
 	<key>CFBundleVersion</key>
-	<string>c2025d94-2019-10-26</string>
+	<string>451f21cb-2020-12-19</string>
 	<key>CGDisableCoalescedUpdates</key>
 	<true/>
 	<key>LSMinimumSystemVersion</key>