minor remaining issue with usemap in XHTML 1.1 DTD

The XHTML 1.1 DTD contains this comment:

  "It is considered an error for the element pointed to by a
  usemap IDREF to occur in anything but a <map> element."

http://www.w3.org/MarkUp/2010/PER-xhtml-modularization-20100213/dtd_module_defs.html#a_module_Image

I realize that comment is non-normative, but in the interest of
preventing confusion, it would seem to be helpful to change
"IDREF" to "URIREF".

  --Mike

-- 
Michael(tm) Smith
http://people.w3.org/mike