Check interpeter for potential long-running loops

In NeilFraser/JS-Interpreter#207, @NeilFraser notes that many of the `Array.prototype` methods have potential long-running or infinite loops—e.g., `Array.prototype.lastIndexOf.call({0: true, length: 'Infinity'}, true);` takes forever to complete.

CodeCity's `interpreter.js` uses different implementations of most of these methods, but is vulnerable to the same issue.

The interpreter should be checked carefully for loops; _every_ loop could potentially hang the interpreter of a malicious user found a way to cause it to run a large number of times. Every loop that is subject to user control over the number of iterations should be modified to check for thread timeouts. This includes almost all of the `Array.prototype` methods as well as things like `Function.prototype.apply` and even `Interpreter.prototype.pseudoToNative`. (Loops in places like `Object.prototype.isPrototypeOf` and `Interpreter.PropertyIterator.prototype.next` are probably OK, because in those case the number of iterations are bounded by the number of allocated objects in the database or the number of keys in an object.)