Small documentation fixes.

    2013-06-11  Didier Verna  <didier@didierverna.net>

	* symbol.lisp (finalize-definitions): Update docstring and comment.
Fix one too broad method definition.

2013-06-11  Didier Verna  <didier@didierverna.net>

    * symbol.lisp (document): Specialize the FUNCOID method on
    FUNCTION-DEFINITION only.
Initial support for documenting setf-expanders.

2013-06-11  Didier Verna  <didier@didierverna.net>

	* item/symbol.lisp (funcoid-definition): New slot SETF-EXPANDER.
	(finalize-definitions): Fill it in for macros and (generic)
	functions in the case of short forms.
	* doc/symbol.lisp (render-@defunoid): Document a potential
	setf-expander (docstring and reference to the setter function).
Support long forms of setf expanders.

2013-06-12  Didier Verna  <didier@didierverna.net>

	* src/item/symbol.lisp (funcoid-definition): Update docstring to
	reflect handling of long forms of setf expanders.
	(finalize-definitions): Handle long forms of setf expanders.
	* src/doc/symbol.lisp (render-@defunoid): Document long forms of
	setf expanders.
Render anonymous setf expanders through Texinfo's @deffn macro.

2013-06-12  Didier Verna  <didier@didierverna.net>

	* src/util/texi.lisp (@defsetf): New macro.
	* src/doc/symbol.lisp (render-@defunoid): Use it.
Improve juncture of readers and writers methods and (generic) functions.

We don't need the lambda lists to be EQUAL since they are advertised along the
names anyway (so it doesn't hurt if they are different).

2013-06-12  Didier Verna  <didier@didierverna.net>

	* src/doc/symbol.lisp (document): Don't test for equality of
	lambda lists for (generic) accessors functions and methods.