WTS: Set onSOL state when newlines are buffered for future separators.

* Try this and look at onSOL state for the A-node.

echo 'x\n<a rel="mw:ExtLink" href="http://google.com">http://google.com</a>' | node parse --html2wt --trace wts

  Before this patch, the serializer was left in a onSOL=false state.
  However, in reality, the A-node is being processed in a SOL context.

  This was happening because trailing newlines are stripped from
  text nodes and buffered for use when emitting a separator between
  this text node and the following element. In this patch, we set
  state.onSOL to true when this happens. The patch also records a
  caveat for when this might be inaccurate.

* Changes output of html2wt and html2html for one test (which was
  already failing previously). Parsoid should be ignoring this test.

Change-Id: Id580bb185804c25f4bb9da454d5790137ad4fed2
Merge "WTS: Set onSOL state when newlines are buffered for future separators."