[css-exclusions] Refer to css-position-3

In "position: fixed;" the 'fixed' keyword is from css-position-3.

Author: ericwilligers

css-exclusions-1/Overview.bs

@@ -17,6 +17,9 @@ Editor: Alan Stearns, Adobe, astearns@adobe.com, w3cid 46659
 Abstract: CSS Exclusions define arbitrary areas around which inline content ([[!CSS21]]) can flow. CSS Exclusions can be defined on any CSS block-level elements. CSS Exclusions extend the notion of content wrapping previously limited to floats.
 Ignored Terms: div, dl, dfn
 </pre>
+<pre class=link-defaults>
+spec:css-position-3; type:value; text:fixed
+</pre>
 
 <style type="text/css">
   .singleImgExample {