Finish pdbtrack integration cleanup, settling missing-functions

Finish pdbtrack integration cleanup, settling missing-functions
byte compiler warnings appropriately.

* progmodes/python.el (python-point): Remove this - beginning-of-line was
all that was necessary for `python-pdbtrack-overlay-arrow'.
(python-end-of-def-or-class, python-beginning-of-def-or-class)
(python-goto-initial-line): Drop these - they were only needed for
python-point.
(python-comint-output-filter-function): Use condition-case and
beginning-of-line directly, instead of python-mode.el functions
which require all sorts of baggage.
(point-safe): Unnecessary - we're using condition-case directly,
instead.
(python-execute-file): Include for python-shell, which i'm leaving
in keeping despite it being unnecessary for pdb tracking.