- Create optional with ~ instead of ?. return io::EOF?; becomes return io::EOF~.

- Deprecated use of `?` to create optional.

test/test_suite/assert/unreachable_in_macro.c3t

@@ -16,7 +16,7 @@ faultdef ABC;
 macro test()
 {
   if (false) return;
-  return ABC?;
+  return ABC~;
   unreachable();
 }