python.el: Improved shell font lock respecting markers.

python.el: Improved shell font lock respecting markers.

Fixes: debbugs:19650
* lisp/progmodes/python.el
(python-shell-font-lock-get-or-create-buffer): Use special buffer name.
(python-shell-font-lock-with-font-lock-buffer): Enable font lock.
(python-shell-font-lock-post-command-hook): Fontify by copying text
properties from fontified buffer to shell, keeping markers unchanged.
(python-shell-font-lock-turn-off): Fix typo.
(python-util-text-properties-replace-name): Delete function.