Undo changes to target attribute/prop on a element

Keep it specified as an animatable attribute
& an SVGAnimatedString DOM property,
as implemented in all major browsers,
unless/until we can get agreement to change implementations.

PS, If that agreement happens, in addition to reverting this commit,
we also need to change the "yes" animatable in the table in linking.html.

master/definitions.xml

@@ -16,7 +16,7 @@
       interfaces='SVGAElement'>
     <x:contentmodel xmlns='http://www.w3.org/1999/xhtml'>Descriptive content, plus any element or text allowed by its parent's content model, except for another a element.  If the parent is a switch element, use the content model of the nearest ancestor that isn't a switch.</x:contentmodel>
     <attribute name='href' href='linking.html#AElementHrefAttribute' animatable='yes'/>
-    <attribute name='target' href='linking.html#AElementTargetAttribute' animatable='no'/>
+    <attribute name='target' href='linking.html#AElementTargetAttribute' animatable='yes'/>
     <attribute name='download' href='linking.html#AElementDownloadAttribute' animatable='no'/>
     <attribute name='ping' href='linking.html#AElementPingAttribute' animatable='no'/>
     <attribute name='rel' href='linking.html#AElementRelAttribute' animatable='no'/>

master/linking.html

@@ -1140,7 +1140,7 @@ <h3 id="InterfaceSVGAElement">Interface SVGAElement</h3>
 
 <pre class="idl">[Exposed=Window]
 interface <b>SVGAElement</b> : <a>SVGGraphicsElement</a> {
-  attribute DOMString <a href="linking.html#__svg__SVGAElement__target">target</a>;
+  [SameObject] readonly attribute <a>SVGAnimatedString</a> <a href="linking.html#__svg__SVGAElement__target">target</a>;
   attribute DOMString <a href="linking.html#__svg__SVGAElement__download">download</a>;
   attribute USVString <a href="linking.html#__svg__SVGAElement__ping">ping</a>;
   attribute DOMString <a href="linking.html#__svg__SVGAElement__rel">rel</a>;