Merge pull request #808 from davidlazar/master

Improvements to Haddock reader
Docx writer: Use Compact style for Plain block elements.

This differentiates between tight and loose lists.
Closes #775.
LaTeX reader: Support `\textasciitilde`, `\textasciicircum`.

Closes #810.
Haddock reader: derive Show for Token, making debugging easier.
Haddock reader: leaving Space alone in @...@ seems more semantically correct.
Haddock reader: add tests.