auto merge of #10849 : adridu59/rust/patch-css, r=alexcrichton

rustdoc:
- fix search-bar layout

doc: CSS:
- switch to native pandoc toc depth
- rm some dead code
- clamp width to be readable (we're not Wikipedia!)
- don't background-color titles, it's bloating
- make syntax-highlighting colors inline with rust-lang.org
- space indents

@alexcrichton

src/librustdoc/html/layout.rs

@@ -58,11 +58,13 @@ pub fn render<T: fmt::Default, S: fmt::Default>(
 
     <nav class=\"sub\">
         <form class=\"search-form js-only\">
-            <input class=\"search-input\" name=\"search\"
-                   autocomplete=\"off\"
-                   placeholder=\"Search documentation...\"
-                   type=\"search\" />
             <button class=\"do-search\">Search</button>
+            <div class=\"search-container\">
+                <input class=\"search-input\" name=\"search\"
+                       autocomplete=\"off\"
+                       placeholder=\"Search documentation...\"
+                       type=\"search\" />
+            </div>
         </form>
     </nav>