Deprecate ASMifiable and Textifiable. Also remove some deprecated, unused code...

Deprecate ASMifiable and Textifiable. Also remove some deprecated, unused code. This removal might break some existing code, but I think the probability is very low. Indeed the 'buf' field was already changed previously to 'null', and is final. And Printer.appendString does not seem to be used, at least in open source projects: https://www.google.fr/search?q=%22printer.appendstring%22.