Rust: Add parenthesis example to test.

Author: geoffw0

rust/ql/test/query-tests/unusedentities/UnreachableCode.expected

@@ -26,3 +26,6 @@
 | unreachable.rs:156:3:156:17 | ExprStmt | This code is never reached. |
 | unreachable.rs:162:4:162:18 | ExprStmt | This code is never reached. |
 | unreachable.rs:165:2:165:16 | ExprStmt | This code is never reached. |
+| unreachable.rs:171:10:171:16 | ParenExpr | This code is never reached. |
+| unreachable.rs:171:11:171:15 | ParenExpr | This code is never reached. |
+| unreachable.rs:171:12:171:14 | ParenExpr | This code is never reached. |

rust/ql/test/query-tests/unusedentities/main.rs

@@ -257,6 +257,5 @@ fn main() {
 	unreachable_panic();
 	unreachable_match();
 	unreachable_loop();
-
-	println!("lets use result {}", parameters(1, 2, 3));
+	unreachable_paren();
 }

rust/ql/test/query-tests/unusedentities/unreachable.rs

@@ -166,3 +166,7 @@ fn unreachable_loop() {
 	do_something();
 	do_something();
 }
+
+fn unreachable_paren() {
+	let _ = (((1))); // SPURIOUS: unreachable (x3)
+}