update elements and fix some bugs

lib/src/prism/plugins/show-language/prism-show-language.js

 (function(){
 
-if (!self.Prism) {
+if (typeof self === 'undefined' || !self.Prism || !self.document) {
         return;
 }
 
-var Languages = {
-        'csharp': 'C#',
-        'cpp': 'C++'
-};
+// The languages map is built automatically with gulp
+var Languages = /*languages_placeholder[*/{"css":"CSS","clike":"C-like","javascript":"JavaScript","abap":"ABAP","actionscript":"ActionScript","apacheconf":"Apache Configuration","apl":"APL","applescript":"AppleScript","aspnet":"ASP.NET (C#)","autoit":"AutoIt","autohotkey":"AutoHotkey","basic":"BASIC","csharp":"C#","cpp":"C++","coffeescript":"CoffeeScript","css-extras":"CSS Extras","fsharp":"F#","glsl":"GLSL","http":"HTTP","inform7":"Inform 7","latex":"LaTeX","lolcode":"LOLCODE","matlab":"MATLAB","mel":"MEL","nasm":"NASM","nginx":"nginx","nsis":"NSIS","objectivec":"Objective-C","ocaml":"OCaml","php":"PHP","php-extras":"PHP Extras","powershell":"PowerShell","jsx":"React JSX","rest":"reST (reStructuredText)","sas":"SAS","sass":"Sass (Sass)","scss":"Sass (Scss)","sql":"SQL","typescript":"TypeScript","vhdl":"VHDL","vim":"vim","wiki":"Wiki markup","yaml":"YAML"}/*]*/;
 Prism.hooks.add('before-highlight', function(env) {
         var pre = env.element.parentNode;
         if (!pre || !/pre/i.test(pre.nodeName)) {
                 return;
         }
-        var language = Languages[env.language] || env.language;
+        var language = Languages[env.language] || (env.language.substring(0, 1).toUpperCase() + env.language.substring(1));
         pre.setAttribute('data-language', language);
+
+        /* check if the divs already exist */
+        var sib = pre.previousSibling;
+        var div, div2;
+        if (sib && /\s*\bprism-show-language\b\s*/.test(sib.className) &&
+                sib.firstChild &&
+                /\s*\bprism-show-language-label\b\s*/.test(sib.firstChild.className)) {
+                div2 = sib.firstChild;
+                if (div2.getAttribute('data-language') !== language) {
+                        div2.setAttribute('data-language', language);
+                        div2.innerHTML = language;
+                }
+        } else {
+                div = document.createElement('div');
+                div2 = document.createElement('div');
+
+                div2.className = 'prism-show-language-label';
+                div2.setAttribute('data-language', language);
+                div2.innerHTML = language;
+
+                div.className = 'prism-show-language';
+                div.appendChild(div2);
+
+                pre.parentNode.insertBefore(div, pre);
+        }
 });
 
 })();