hgweb: add removeByClassName javascript function

It removes all elements with specified class name from the document.

mercurial/templates/static/mercurial.js

@@ -329,6 +329,13 function makeRequest(url, method, onstar
     return xfr;
 }
 
+function removeByClassName(className) {
+    var nodes = document.getElementsByClassName(className);
+    while (nodes.length) {
+        nodes[0].parentNode.removeChild(nodes[0]);
+    }
+}
+
 function docFromHTML(html) {
     var doc = document.implementation.createHTMLDocument('');
     doc.documentElement.innerHTML = html;