**background**
TS 2.6 introduces a new strict function checking mode. This can catch many common mistakes such as patterns like this:

```js
function on(callback: (Base) => void) { ... }

on((e: Sub) =>  {...});
```

This does an implicit cast in the call to `on`. With strict function checking, this is now flagged as an error

**Change**
This change fixes dom.on so that it works with strict function checking. This done by making it generic so that the type of the event taken in the callback can be inferred from the callback itself.

WIth strictFunctions, the callback can no longer use implicit casts to a subclass for parameter types. This pattern was widely used with `.on` event callbacks in the dom

rename startupTimer to performance, support mark and measure, drop promise support, add more marks to slowly phase out old timers