Fixed: Data should not be converted into JSON in CKEDITOR.ajax.post.
Updated codesnippetgeshi to latest CKEDITOR.ajax.post API.
Removed obsolete Content-type header from CKEDITOR.ajax.post.
Extended CKEDITOR.ajax.post with optional Content-type header. Added docs for the method.
Code refactoring: converted function expressions into function declarations and fixed code indentation in AJAX plugin.
Added undo to sample toolbars.
Fixed updateSnapshot to prevent broken undoManager stack.