Relax the need to escape every { in <hint> <message>

In the Java <hint> <message>, every `{` beeds to be escaped as `\ {`. That doesn't seem like a good UX to me. The hints often contain a code examples.

I think that we should revisit how the Rewrite construct

is matched.

How about not matching any { not followed by * or alnum? Or followed by a whitespace?

We could do it simply by escaping such cases automatically before sending the string to evaluation.