add server upload buttons and Ctrl-S bindings to mode_editor

in combination with PUT support in ./static.py (or whatever other web server)
this allows people to save both the highlighting rules and the demo documents right
from the mode editor for a better workflow.

lib/ace/lib/net.js

@@ -22,6 +22,19 @@ exports.get = function (url, callback) {
     xhr.send(null);
 };
 
+exports.put = function (url, data, callback) {
+    var xhr = new XMLHttpRequest();
+    xhr.open('PUT', url, true);
+    xhr.onreadystatechange = function () {
+        //Do not explicitly handle errors, those should be
+        //visible via console output in the browser.
+        if (xhr.readyState === 4) {
+            callback(xhr.responseText);
+        }
+    };
+    xhr.send(data);
+};
+
 exports.loadScript = function(path, callback) {
     var head = dom.getDocumentHead();
     var s = document.createElement('script');