UB2 now signs and notarizes, upgraded to SDL 2.0.16

Also works on Apple Silicon. Specific signing values are in a non-committed file, and the ub2 script only notarizes if a "notarize" flag is passed in on the command line.

NOTE: the SDL dylib currently only has x86_64 and arm64, will need extra work to graft those back in and keep the Notary service happy.

misc/xcode/ioquake3/ioquake3.entitlements

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>com.apple.security.cs.allow-unsigned-executable-memory</key>
+	<true/>
+</dict>
+</plist>