Since you can accomplish the same thing with a `page/render` hook (which should be better documented on my part... :P), I think we should leave the Current-User stuff out of the core. Here's the same thing as a web hook:

	<?php // apps/myapp/handlers/hook/add-current-user-header.php

	if (is_object (User::current ())) {
		$this->header ('Current-User: ' . User::val ('name'));
	}

	?>

And in `conf/config.php`'s `[Hooks]` section:

	page/render[] = myapp/hook/add-current-user-header

The rest of the pull request is very close to being ready to merge (and looking good! :)), so I think avoiding the potential privacy issues around this one is for the best.