Handle pre while emtting BEGIN_SEP, IE_SEP, and END_SEP.

* Sloppy coding on my part -- this should have been caught in
  commit 57b5652d when I fixed this exact same bug in another
  place.  There are 3 places where separators are emitted and
  all 3 needed indent-pre check and I added one in that commit
  but missed the last one.

* Fixes RTing of:
----
 <span>a</span>
 <span>b</span>
----

* No change in parser tests (TODO: Add more)

Change-Id: I06d95954046fc98bcfe564948a01dd96a09f9a6e