Mark old SVG interfaces as obsolete (#240)

* Mark SVGCursorElement as deprecated

Removed in w3c/svgwg@94eb871 but still available in WebKit so marking it as deprecated rather than obsolete
https://developer.apple.com/documentation/webkitjs/svgcursorelement

* fixup cursor

* Mark SVGEvent as obsolete

Removed in https://dev.w3.org/cvsweb/SVG/profiles/1.1F2/master/interact.html.diff?r1=1.15;r2=1.16

* Mark SVGStylable as obsolete

Per w3c/svgwg@0f5bb90

* Mark SVGTransformable as obsolete

Per w3c/svgwg@6ce402c

files/en-us/web/api/svgcursorelement/index.html

@@ -8,7 +8,7 @@
   - SVG
   - SVG DOM
 ---
-<div>{{APIRef("SVG")}}</div>
+<div>{{deprecated_header}}{{APIRef("SVG")}}</div>
 
 <p>The <strong><code>SVGCursorElement</code></strong> interface provides access to the properties of {{ SVGElement("cursor") }} elements, as well as methods to manipulate them.</p>
 

files/en-us/web/api/svgevent/index.html

@@ -7,7 +7,7 @@
   - SVG
   - WebAPI
 ---
-<div>{{APIRef("SVG")}}</div>
+<div>{{obsolete_header}}{{APIRef("SVG")}}</div>
 
 <p>The {{domxref("SVGEvent")}} interface represents the event object for most SVG-related events.</p>
 

files/en-us/web/api/svgstylable/index.html

@@ -9,9 +9,8 @@
   - SVG
   - SVG DOM
 ---
-<div>{{APIRef("SVG")}}</div>
+<div>{{obsolete_header}}{{APIRef("SVG")}}</div>
 
-<h2 id="SVG_stylable_interface">SVG stylable interface</h2>
 
 <p>The <code>SVGStylable</code> interface is implemented on all objects corresponding to SVG elements that can have {{ SVGAttr("style") }}, {{SVGAttr("class")}} and presentation attributes specified on them.</p>
 

files/en-us/web/api/svgtransformable/index.html

@@ -9,9 +9,8 @@
   - SVG
   - SVG DOM
 ---
-<div>{{APIRef("SVG")}}</div>
+<div>{{obsolete_header}}{{APIRef("SVG")}}</div>
 
-<h2 id="SVG_transformable_interface">SVG transformable interface</h2>
 
 <p>Interface <code>SVGTransformable</code> contains properties and methods that apply to all elements which have attribute {{ SVGAttr("transform") }}.</p>