Make python.el work with IPython automatically.

Make python.el work with IPython automatically.

* lisp/progmodes/python.el:
(python-shell-completion-setup-code): New value supporting iPython.
(python-shell-completion-string-code): New value supporting iPython.
(python-shell-completion-get-completions): Use them.
(python-shell-completion-module-string-code): Make obsolete.
(python-shell-prompt-input-regexps)
(python-shell-prompt-output-regexps): Add safeguard for ipdb.
(python-shell-output-filter): Fix comment typo.

* test/automated/python-tests.el:
(python-util-clone-local-variables-1): Fix test.

Fixes: debbugs:15510