tests: add test case for reference to cast

Author: fw-immunant

tests/casts/src/casts.c

@@ -30,4 +30,7 @@ void cast_stuff(void) {
 
         bool b = true;
         float x15 = b;
+
+        // reference applied to a cast requires parens on Rust side
+        int * x = &(int){0};
 }