Sort definitions extracted from the .asd file.

2013-06-20  Didier Verna  <didier@didierverna.net>

	* src/doc/asdf.lisp (add-files-node): Sort system file definitions.
Add missing DOCUMENT method for generic writers.
This makes their documentation reference back to a corresponding reader if
any.

2013-06-20  Didier Verna  <didier@didierverna.net>

	* src/doc/symbol.lisp (document (generic-writer-definition)):
	New method.
TODO update.

2013-06-20  Didier Verna  <didier@didierverna.net>

	* TODO: Update some bits. Remove the setf expander part now that
	it's done.