Robust shell syntax highlighting. (Bug#18084, Bug#16875)

Robust shell syntax highlighting.  (Bug#18084, Bug#16875)

* lisp/progmodes/python.el:
(python-shell-prompt-input-regexps): Add iPython block prompt.
(python-shell-output-syntax-table): Delete var.
(python-shell-font-lock-with-font-lock-buffer): New macro.
(python-shell-font-lock-get-or-create-buffer)
(python-shell-font-lock-kill-buffer)
(python-shell-font-lock-cleanup-buffer)
(python-shell-font-lock-post-command-hook)
(python-shell-font-lock-turn-off): New functions.
(python-shell-font-lock-turn-on): New function.
(inferior-python-mode): Use it.
(python-shell-font-lock-toggle): New command.
(python-shell-font-lock-enable): Rename from
python-shell-enable-font-lock.
(run-python-internal): Use it.
(python-shell-font-lock-comint-output-filter-function): New function.
(python-shell-comint-end-of-output-p): New function.
(python-shell-output-filter): Use it.
(python-util-comint-last-prompt): New function.
(python-util-text-properties-replace-name): New function.