Some more selective serializer fixes

* Fixes a bug in WTS that serialized meta elements that were child nodes of
  stx:html- marked elements using the HTML tag handler. This caused stray
  <meta/> tags in the output.

* Expand source ranges unconditionally if text node is no IEW.

* Treat node with deleted-child diff marker as modified if no children are
  remaining. If there are children, we normally insert another diff marker
  with deleted-before flag at the relevant child position.

With this patch 356 additional selser tests are green, with no changes to
other test modes.

Change-Id: I468a47f85518c303015eeae68f8b340ce704f924
Merge "Some more selective serializer fixes"