Add a timeout for statements

[0x0elliot]

Since DoS attacks are a concern, I wonder if a timeout statement would help here.

if there are better ways to tackle it, a thread would definitely help for this.

[danthedeckie]

Fundamentally, yes.

Should that be a core part of simpleeval, or rather a separate package... something I've been pondering for a while.

Or if it's an easy / tiny thing, then could it just be a "recommended pattern" in the readme?

ideas?