* minibuffer.el (completion-at-point-functions): New var.

* minibuffer.el (completion-at-point-functions): New var.
(completion-at-point): New command.
* indent.el (indent-for-tab-command): Handle the new `complete' behavior.
* progmodes/python.el (python-mode-map): Use completion-at-point.
(python-completion-at-point): Rename from python-partial-symbol and
adjust for use in completion-at-point-functions.
(python-mode): Setup completion-at-point for Python completion.
* emacs-lisp/lisp.el (lisp-completion-at-point): New function
extracted from lisp-complete-symbol.
(lisp-complete-symbol): Use it.
* emacs-lisp/lisp-mode.el (emacs-lisp-mode): Use define-derived-mode,
setup completion-at-point for Elisp completion.
(emacs-lisp-mode-map, lisp-interaction-mode-map): Use completion-at-point.
* ielm.el (ielm-map): Use completion-at-point.
(inferior-emacs-lisp-mode): Setup completion-at-point for Elisp completion.
* progmodes/sym-comp.el: Move to...
* obsolete/sym-comp.el: Move from progmodes.