* pay attention to import specs!

* instances: list relevant instances in the documentation for classes and
  datatypes.

* parse module headers, augment Interface with info from header

* include file revision info in module headers

* handle scoped type variables in the parser

* Allow fully hiding modules from the output

* Add a link to the defining location of a re-exported entity

* fixities

* we don't deal with records properly - exporting record selectors etc.

* doc strings for: function arguments

* remove the s/r conflicts I added to the grammar

* check handling of special types ([], (), (,) etc.)

* Horizontal lines?

* Short contents at the top of each module?

* enhance the doc string parser:
	* @...@ for monospaced text
	* an apostrophe inside a string shouldn't be considered to be a quote
	* the lexer should deal with <...> so that special chars
	  inside don't need to be escaped.

* Handle parse errors better in doc strings

* Do proper dependency analysis rather than relying on laziness to
  sort it out.

* Do the unlitting/CPPing from Haddock itself

* clean up the layout: don't use table cellspacing, use CSS instead

* omit the synopsis for modules with no doc

* named chunks of documentation?