cleaned up ids, added direct rust doc search

Search functionality uses both duckduckgo for site wide doc search
and the rust specific documentation search @

http://doc.rust-lang.org/core/?search=unwrap_or_else

src/doc/not_found.md

@@ -13,9 +13,10 @@ Some things that might be helpful to you though:
 
 ## Search
 * <form action="https://duckduckgo.com/">
-    <input type="text" id="code.search" name="q" size="80"></input>
+    <input type="text" id="site-search" name="q" size="80"></input>
     <input type="submit" value="Search DuckDuckGo">
 </form>
+* Rust doc search: <span id="core-search"></span>
 
 ## Reference
 * [The Rust official site](http://rust-lang.org)
@@ -25,19 +26,38 @@ Some things that might be helpful to you though:
 * [The standard library](http://doc.rust-lang.org/std/)
 
 <script>
-function populate_search_box() {
+function get_url_fragments() {
-
     var last = document.URL.split("/").pop();
     var tokens = last.split(".");
     var op = [];
     for (var i=0; i < tokens.length; i++) {
-        if (tokens[i].indexOf("#") == -1) 
+        var t = tokens[i];
-            op.push(tokens[i]);
+        if (t == 'html' || t.indexOf("#") != -1) {
+            // no html or anchors
+        } else {
+            op.push(t);
+        }
     }
+    return op;
+}
 
-    var search = document.getElementById('code.search');
+function populate_site_search() {
+    var op = get_url_fragments();
+
+    var search = document.getElementById('site-search');
     search.value = op.join(' ') + " site:doc.rust-lang.org";
 }
-populate_search_box();
+
+function populate_rust_search() {
+    var op = get_url_fragments();
+    var lt = op.pop();
+
+    // #18540, use a single token
+
+    var search = document.getElementById('core-search');
+    search.innerHTML = "<a href=\"http://doc.rust-lang.org/core/?search=" + lt + "\">" + lt + "</a>";
+}
+populate_site_search();
+populate_rust_search();
 </script>