The old one had various issue, for instance it failed to parse "#hello", and could mis-interpret lines starting with "=". The new one is more robust and handles optional spaces better.

it's useful for the (future) tests being able to compare lines.

we need to terminate the line on the given stream, not on *standard-output*!

I had this in my local tree for a while and forgot to commit them! Since they're here, it'd be a waste to just delete it, even if the ui stuff may not stay around in the long run.

Add blockquote support.