add quads:clear() method

doc/index.html

@@ -2589,6 +2589,7 @@ <h3 id="am.quads" class="func-def">am.quads(n, spec [, usage])</h3>
 <li>a view containing the values for the elements As with the <a href="#view:set"><code>view:set</code></a> method, if the attribute is a vector, a table of numbers is also accepted. The quad number (starting at 1) is returned.</li>
 </ul></li>
 <li><code>remove_quad(n [,count])</code>: Removes <code>count</code> quads starting with the <code>n</code>th. <code>count</code> is 1 if omitted.</li>
+<li><code>clear()</code>: Removes all quads.</li>
 <li>Additionally methods are created for each attribute of the form <code>quad_&lt;attribute name&gt;</code> that can be used to update the value of a quad attribute. The signature of the method is: <code>quad_attr(n, values)</code> where <code>n</code> is the quad number and <code>values</code> has the same meaning as in the <code>add_quad</code> method.</li>
 </ul>
 <p>Default tag: <code>&quot;quads&quot;</code>.</p>

doc/scene_nodes.md

@@ -1128,6 +1128,7 @@ Methods:
   The quad number (starting at 1) is returned.
 - `remove_quad(n [,count])`: Removes `count` quads starting with the `n`th.
   `count` is 1 if omitted.
+- `clear()`: Removes all quads.
 - Additionally methods are created for each attribute
   of the form `quad_<attribute name>` that can be
   used to update the value of a quad attribute.

lua/shapes.lua

@@ -108,6 +108,10 @@ function am.quads(capacity, spec, usage)
     function bind_node:get_num_quads()
         return n
     end
+    function bind_node:clear()
+        n = 0
+        draw_node.count = 0
+    end
     bind_node:tag"quads"
     return bind_node
 end