1. First You Have Firefox Browser and then Install Greasemonkey script on your Firefox browser with below link.
Now Click on add to firefox and then install.
Restart the Firefox after successful installation of add on, and you will find the Monkey icon in bottom right corner of your firefox window. (Status Bar)
2. Click on the below link and install the User script 'Blogger - HTML encode on post edit' to blogger.
The script will add the new button at the bottom of your new post area. It encodes the selected text so that it can be posted as plain text in Blogger.It will look like the Below image.
If you want to encode some code select it and cick on 'HTML ENCODE SELECTION' button.
Finally Your code will look like as given below after being encoded.Now you can publish your post and see the result.
That's it ! Now your post with xml source code.