While setting tsr for tokens, handle single-line dt-dds correctly.

* ":;a:b" was not being handled correctly by the list handler
  while setting tsr for the ":b" dd token since this case looked
  identical to the multi-line dt-dd case ":;a\n::b" in the list
  handler.
* Added a single-line-dtdd flag in the tokenizer on the dd token
  to recognize this difference and use that to set tsr correctly.
* No change in parser tests or dsr warnings (TODO: add more tests)
* Fixes RT errors on en:Waco YKS

Change-Id: I7d5a770de664897d0a41ebc650c12b112fb32b32