Update livepreview for new Ace.

lib/gollum/frontend/public/gollum/livepreview/js/livepreview/livepreview.js

@@ -172,7 +172,8 @@ var previewSet = function( text ) {
   }
 };
 
-var languages = [ 'c_cpp', 'clojure', 'coffee', 'coldfusion',
+// 'c', 'c++', 'cpp' are github specific and transformed to c_cpp for Ace.
+var languages = [ 'c', 'c++', 'cpp', 'clojure', 'coffee', 'coldfusion',
  'csharp', 'css', 'diff', 'golang', 'groovy', 'haxe', 'html',
  'java', 'javascript', 'json', 'latex', 'less', 'liquid',
  'lua', 'markdown', 'ocaml', 'perl', 'pgsql', 'php', 'powershell',
@@ -205,9 +206,14 @@ function getLang( language ) {
 }
 
 function highlight( element, language ) {
-  var data = element.innerHTML;
+  // Highlighting requires .innerText not
+  // .innerHTML. It's the difference between
+  // '>' and '>'.
+  // Firefox does not support innerText.
+  var data = element.innerText || element.textContent;
   var mode = getLang( language );
-  var color = staticHighlight.render( data, mode, githubTheme );
+  // input, mode, theme, lineStart, disableGutter
+  var color = staticHighlight.render( data, mode, githubTheme, 1, true );
 
   var newDiv = doc.createElement('div');
   newDiv.innerHTML = color.html;
@@ -257,6 +263,23 @@ var makePreviewHtml = function () {
       // the syntax for code highlighting means all code, even one line, contains newlines.
       if ( txt.length > 1 && codeHTML.match( /\n/ ) ) {
         var declaredLanguage = txt[ 1 ];
+        var aceMode = declaredLanguage;
+
+        // GitHub supports 'c', 'c++', 'cpp'
+        // which must trigger the 'c_cpp' mode in Ace.
+        if ( declaredLanguage === 'cpp' ) {
+          aceMode = 'c_cpp';
+        }
+
+        // '`c++'.split( /\b/ )
+        // ["`", "c", "++"]
+        if ( declaredLanguage === 'c' ) {
+          aceMode = 'c_cpp';
+          if ( txt.length > 2 && txt[ 2 ].substring( 0, 2 ) === '++' ) {
+            declaredLanguage += '++';
+          }
+        }
+
         // txt[0] must be '`'
         // txt[0] = '`'; txt[1] = 'ruby'
         if ( txt[ 0 ] !== '`' || $.inArray( declaredLanguage, languages ) === -1 ) {
@@ -268,7 +291,7 @@ var makePreviewHtml = function () {
         // length + 1 for the marker character.
         element.innerHTML = codeHTML.substring( declaredLanguage.length + 1 ).trim();
         // highlight: element
-        highlight( element, declaredLanguage );
+        highlight( element, aceMode );
       } else {
         // Highlighting is not for `code` inline syntax. For example `puts "string"`.
         skipped++;