[css-text-decor-3] specification should clearly identify changes from CSS 2.1

http://dev.w3.org/csswg/css-text-decor-3/#line-decoration changes
the rules for z-ordering of underlines and overlines, relative to
the text, from CSS 2.1's rules.  (They used to be underneath the
text; now they are on top of the text.)  This should be explicitly
identified in the body of the specification as a change from CSS
2.1.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂