Additional tweaks and fixes to separator emitting in WTS.

* Renamed emittedSeparator to emittedSeparatorFromSrc for clarity.
* Fixed emitNLs in SOL mode to not buffer -- buffering only needed
  in EOL mode.  In SOL mode, we either skip if separator has been
  emitted from source, or emit if not.
* Fixed emitNLs to tell selser that the nls are 'separator' content.
* Fixed emitSeparator to not emit separator when in token collection
  mode -- the separator is converted to a regular token.  Fixes
  RTing of wikitext like this:
----
[[File:boo|thumb|bar [[foo]]   [[baz]]  [[bar]] ]]
----
  and eliminates RT errors in en:Barack Obama.

Change-Id: I27c3351ecae3bd4150c8cd77c2bbe4195d78d2cb
Merge "Additional tweaks and fixes to separator emitting in WTS."