Add support for lydell’s fork of elm/virtual-dom

[lydell]

This makes Lamdera work with my fork of elm/virtual-dom. More information coming soon. No need to merge this yet.

Lamdera copies some functions from elm/virtual-dom, to make modifications to them. My fork of elm/virtual-dom also changes those functions. This PR copies those changes, and supports both the original version and my fork by if-ing on whether _VirtualDom_wrap exists (one of the new functions in my fork, arbitrary choice). This is for _VirtualDom_applyPatches, _VirtualDom_diff and _VirtualDom_applyPatches.

My fork also removes _VirtualDom_equalEvents, which Lamdera references. The solution is to just define the variable.

Finally, I added the data-elm attribute to <pre id="elm"></pre>. My fork only virtualizes elements with data-elm, for better compatibility with third-party scripts.

lamdera live assumes that initializing the Elm app removes that element, and displays a message in it otherwise:

compiler/extra/live.js

Lines 124 to 126 in 6415988

	if (document.getElementById(elid)) {
	document.getElementById(elid).innerText = 'This is a headless program, meaning there is nothing to show here.\n\nI started the program anyway though, and you can access it as `app` in the developer console.'
	}

By adding data-elm to it, Elm will virtualize it, and then realize that it isn’t needed and remove it (just like before).

Note: I have only tested lamdera live. I have not tested a production upgrade between two app versions, but I’ve gone through the code and it looks like it should™️ work.