Slightly simplify crFinishFree{,V}.

They're only likely to be useful for freeing a coroutine state
structure, in which case there's no need to reset the line number
(since all such coroutines keep their line number in the state
structure) and the state structure pointer is always called "s".

git-svn-id: svn://svn.tartarus.org/sgt/putty@9632 cda61777-01e9-0310-a592-d414129be87e